SOCIETY OF VECTOR ECOLOGISTS - SOVE folder/journal/sovejournal74-2000/SOVE 1987, VOL 12... · West...

BSOVE 12( 2): 505- 585 ( 1987)

ISSN 0146- 6429

Bulletin of the

SOCIETY OF

VECTOR ECOLOGISTS

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Volume 12, Number 2 December, 1987

BULLETIN OF THE

SOCIETY OF VECTOR ECOLOGISTS

Volume 12- Number 2 December 1987

James P. Webb, Ph.D., Editor Minoo B. Maim, Production Manager

Orange County Vector Control District Environmental Management Branch

13001 Garden Grove Boulevard California State Department of Health ServicesGarden Grove, CA 92643 Los Angeles, CA 90026

EDITORIAL BOARD

Dr. Mir S. Mulla, Chairman,

University of CaliforniaRiverside, CA 92521

Dr. A. J. Adames Dr. J. B. Davies Dr. R. S. Lane Dr. F. J. RadovskyUniversity of Panama Liverpool Sch. of Trop. Med. University of California California Acad. of Sciences

Panama Liverpool, England Berkeley, California San Francisco, California

I) r. A. All Dr. M. S. Dhillon Dr. L. A. Magnarelli Dr. R. E. Ryckman

University of Florida Northwest M.A.D. Conn. Agr. Exp. Station Loma Linda UniversitySanford, Florida Riverside, California New Haven, Connecticut Loma Linda, California

Dr. D. R. Barnard Dr. P. Eisen Dr. C. J. Mitchell Dr. H. I. Scudder

Lone Star Tick Research Lab. Institute of Trop. Medicine Centers for Disease Control California State UniversityPoteau, Oklahoma Antwerp, Belgium Fort Collins, Colorado Hayward, California

Dr. Norbert Becker Dr. R. E. Fontaine Dr. G. R. Mullen Dr. M. W. Service

University of Heidelberg CDC, Public Health Service Auburn University Liverpool Sch. of Trop. Med.Heidelberg, West Germany Atlanta, Georgia Auburn, Alabama Liverpool, England

Dr. H. Briegel Dr. M. L. Goff Dr. S. Nalim Dr. E. S. Tikasingh

University of Zurich University of Hawaii, Manoa Vector Control Research Unit Caribbean Epidemiology Ctr.Zurich, Switzerland Honolulu, Hawaii Ungaran, Indonesia Port of Spain, Trinidad

Dr. P. Carnevale Dr. D. J. Gubler Dr. G. F. O' Meara Dr. G. B. White

O. R. S. T.O. M. CDC, Public Health Service University of Florida, IFAS London Sch. Hyg. Trop. Med.Bobo Diolasso, Burkina Faso San Juan, Puerto Rico Vero Beach, Florida London, England

Dr. G. G. Clark Dr. C. E. Hopla Dr. S. Palchick Dr. S. C. Williams

CDC, Public Health Service University of Oklahoma Metro. Mosq. Cont. Dist. San Francisco State Univ.

San Juan, Puerto Rico Norman, Oklahoma St. Paul, Minnesota San Francisco, California

Dr. W. J. Crans Dr. M. J. Klowden M. A. Parsons Dr. W. J. WrennRutgers University University of Idaho Department of Health University of North DakotaNew Brunswick, New Jersey Moscow, Idaho Columbus, Ohio Grand Forks, North Dakota

Dr. C. Dahl Dr. L. A. Lacey Dr. D. B. Pence

Uppsala University Medical Services Consultants Texas Tech UniversityUppsala, Sweden Arlington, Virginia Lubbock, Texas

Published by the Society of Vector Ecologiststo disseminate pertinent information fromall

facets of the field of Vector Ecology and Related Disciplines

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BULLETIN

OF THE

SOCIETY OF VECTOR ECOLOGISTS

VOLUME 12 DECEMBER, 1987 NUMBER 2

CONTENTS

In Memoriam - Cornelius B. Philip ( 1900- 1987) ivLetter to the Editor

vi

Photograph of the 1st European Region Meeting, Montpellier, FRANCE, 1986 vii

Photograph of the 2nd European Region Meeting, Heidelberg, WEST GERMANY, 1987 viii

Submitted Papers

Laboratory Flight Ability of Aedes triseriatus ( Say) J. L. Clarke, III and W. A. Rowley 505

The Effect of Immature Mosquitoes on Oviposition by Culex pipiens quinquefasciatus and Culisetaincidens ( Diptera: Culicidae) in the Field T. R. Wilmot, S. E. Cope, and A. R. Barr 512

Pattern of Thelytoky Acquisition in Muscidifurax raptor Girault and Sanders ( Hymenoptera:Pteromalidae) E. F. Legner 517

Some Quantitative Aspects of Inheritance in Breeding Synanthropic Fly Parasitoids E. F. Legner 528

Medically Important and Other Ectoparasitic Acarines on Vertebrates from Santa Catalina Island,California S. G. Bennett 534

Scientific Note

The Influence of Host Behavior on Sandfly ( Lutzomyia longipalpis) Feeding Success on LaboratoryMice R. E. Coleman and J. D. Edman 539

Proceedings

1st European SOVE Branch Meeting, Montpellier, FRANCE11- 12 September, 1986

Malaria Transmission in the Three Sites Surrounding the Area of Bobo-Dioulasso ( Burkina Faso): TheSavanna, a Rice Field, and the City V. Robert, P. Gazin, and P. Camevale 541

Contributions to the Ecology of Tahyna Virus in Central Europe J. Pilaski 544

Essais de Modelisation de I:Ingestion des Parlicules par les Larves du Complexe Simulium damnosum:Dip Simuliidae) P. Elsen 554

18th Annual SOVE Conference, University of California, Riverside19- 21 November, 1986

Importance of Vector Overwintering to Disease Maintenance W. C. Reeves 561

The Future Status of Arbovin>ses in North America W. C. Reeves 564

Overwintering Mechanisms of North American Culiseta W. K. Reisen 568

Future Operational Considerations R. D. Sjogren, D. J. Dobbert, and S. Palchick 580

SOVE Symposium, AMCA Annual Meeting, Seattle, Washington31 March, 1987

Manpower Needs in Disease Endemic Countries R. Slooff 584

NUMBER 2 DECEMBER, 1987 VOLUME 12

INMEMORIAM1

Cornelius Becker Philip

1900- 1987

VINO

Cornelius( Neil"} B. Philip died in San Francisco teaches who allowed him to collect insects in the schoolon January 8, 1987, after an illness of several months. yard during study hours. He obtained a Bachelor of

Neil was born in Fort Lupton, Colorado, on June Science degree from the University of Nebraska in12, 1900. His preoccupation with natural •histo y began 1923, and Doctor.of Philosophy degree in entomologyearly in life when he spent countless hours collecting from the University of Minnesota in 1930.insects and other animals. In 1918, he graduated from Prior to completion of his graduate studies, Neil

Long Beach Polytechnic High in California, where his accepted a temporary appointment with the Rockefellerbudding interest in biology had been encouraged by a West African Yellow Fever Commission in Lagos,

The American Society of Parasitologists and the Journal of Parasitology are thanked for permission to reprint thisarticle.

iv

VOLUME 12 DECEMBER, 1987 NUMBER 2

Nigeria, from 1928 to 1929. The following year, he poisoning disease of canines ( with Hadlow and Hughesbegan a long ( 40-1/ 2 years) and highly productive in 1953); and providing the first demonstration ofcareer as a medical entomologist/parasitologist with the canine ehrlichiosis in the United States ( with Ewing inU. S. Public Health Service Rocky Mountain 1964). In 1953, he served as President of the AmericanLaboratory in Hamilton, Montana. During this period Society of Parasitologists, and his presidential addresshe established himself as an authority on ticks and the entitled, " There' s always something new under therickettcial agents they transmit, as well as a world expert ` parasitological' sun ( the unique story of helminth-on Tabanidae ( horse and deer flies). borne salmon poisoning disease" was published in the

In World War II, Neil was assigned to the U. S. Journal of Parasitology two years later.Typhus Commission, and for his efforts he was awarded Neil' s contributions to" tabanidology" were just asthe U. S. Typhus Commission Medal in Manila, 1945, impressive as those to parasitology. He and variousfor" exceptionally meritorious service" rendered during coauthors described no fewer than 550 new taxa ofinvestigations on the epidemiology and control of scrub Tabanidae representing 18 genus-group and 532typhus fever in the southwest Pacific area. species-group names. The latter constitute approxi-

Neil served as director of the Rocky Mountain matey 15 percent of the tabanid species recognizedLaboratory from 1962 to 1964, and shortly before his worldwide.

retirement in 1970, he was presented a Superior Service Besides the honors mentioned above, Neil alsoAward by the Department of Health, Education, and received an Honorary Doctor of Science degree fromWelfare. After retirement, he promptly began his the University of Nebraska ( 1952) and an Outstandingsecond career as a Research Associate in the Alumnus Achievement Award from the University ofDepartment of Entomology at the California Academy Minnesota ( 1960). Moreover, he was an honoraryof Sciences, San Francisco, where he pursued his life- member of both the International Northwestern

long studies of the biosystematics of Tabanidae. While Conference on Diseases in Nature Communicable toa member of the Academy, he participated actively in Man and the American Society of Rickettsiologists andthe Pacific Coast Entomological Society and served as Rickettsial Diseases. Neil' s numerous achievementsits President in 1974. have been documented recently by Jellison and Kohls

During a career that spanned 60 years( 1927- 1987), ( 1973, Exp. Parasitol. 33: 407-423), Collins ( 1976, J.Neil published well over 300 scientific reports and book Parasitol. 62: 504-509), and in a Festschrift compiledchapters, 10 book reviews, and various miscellany, in his honor by Arnaud and Lane ( 1985, Myia 3:including 26 abstracts. Slightly over one-half of his 1- 714).

scientific works involved parasitology and of these, In 1922, Neil met and married Gladys Helen Hill,more than 60 percent concerned ticks, mites, and animal who steadfastly supported his scientific endeavors fordisease agents transmitted by them. A few of his more the next 64 years while raising a family of four children.notable parasitological contributions include the first He is survived by Gladys, two daughters ( Bonnie Deeexperimental proof that yellow fever virus can be and Jo Joyce), two sons( Robert and Gordon), a brothertransmitted by two nondomestic West African ( George), 15 grandchildren, and 6 great-grandchildren.mosquitoes that were subsequently shown to be He also leaves behind many colleagues and friends whonaturally infected ( 1930); the fast demonstration of benefited immeasurably from his constant encourage-epizootic St. Louis encephalitis virus in horses ( with merit as well as his generosity in sharing with them hisCox and Fountain in 1941) and the experimental time and broad knowledge. Moreover, Neil' s keen

susceptibility of horses to this virus ( with Cox and sense of humor and his sage counsel will be missedKilpatrick in 1941); laying the framework for the sorely by all of us who were privileged to have knowncontemporary classification of typhus- like organisms him.

Rickettsiales) ( 1943); demonstrating the efficacy ofChloromycetin® ( Chloramphenicol) for the

prophylaxis and treatment of scrub typhus ( with Robert S. LaneSmadel, Woodward, Ley, Jr., Traub, and Lewthwaite in Department of Entomological Sciences1948); establishing the etiologies of Australian tick University of Californiatyphus ( 1950), Indian tick typhus ( 1952), and salmon Berkeley, California 94720 USA

v

NUMBER 2 DECEMBER, 1987 VOLUME 12

October 9, 1987

Professor Jan Pinowski

Editor, International Studies on Sparrows

Polish Academy of SciencesInstitute of Ecology05- 150 Dziekanow LesnyPOLAND

Dear Professor Pinowski:

I am responding to your request for a reprint of the article by Mitchell, Hayes, and Hughes entitled, " RelativeAbundance of Birds Along Transects in an Endemic Zone of Western Equine Encephalitis Vines Activity inWest Texas," published in 1984 in the Bulletin of the Society of Vector Ecologists 9( 1): 30-36. You will notethat this is essentially the same article that you published without our knowledge under the title, " The RelativeAbundance of Birds Along one Rural and Three Urban Transects in Hale County, Texas," in InternationalStudies on Sparrows 11: 34-36.

I submitted the manuscript to you initially. After retaining the manuscript for several months you wrote thatfunds were no longer available to support publication of International Studies on Sparrows and you recom-mended that I submit the manuscript elsewhere. I did so and the paper was published in the Bulletin of the

Society of Vector Ecologists.

It was a surprise to subsequently receive a copy of your journal, which I thought was defunct, and to find thesame article printed there as well.

I would appreciate it if you would print a copy of this letter in the next issue of your journal. I also am sendinga copy to the Bulletin of the Society of Vector Ecologists for the same purpose.

Sincerely yours,

Carl J. Mitchell, Sc.D.

Chief, Vector Virology LaboratoryCenters for Disease ControlP. O. Box 2087

Fort Collins, CO 80522-2087 USA

CJM/bjb

Enclosures ( 2)

cc: Dr. James P. Webb

vi

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BULL SOC. VECIUR ECOL, 12(2): 505-511DECEMBER, 1987

LABORATORY FLIGHT ABILITY OF AEDES TRISERIATUS ( SAY)1

J. L. Clarke, III 2. 3 and W. A. Rowley'

ABSTRACT: The laboratory ( tethered) flight ability of 416 Aedes triseriatus mosquitoes was evaluated understandard conditions. In the laboratory, Ae. triseriatus was found to be a strong flyer. Mosquitoes( 1 through 6 weeksold) flew between 5,805 m ( week 1) and 9,910 m ( week 3). The average distance flown by 60, 6-weeks-oldmosquitoes was 6,739 m. The length ( duration) of exhaustive flights increased as mosquitoes aged and there wasa correlation between how far mosquitoes flew and the length of their flights. Older mosquitoes were much slowerfliers; 6-weeks-old mosquitoes only half as fast as 5- weeks-old mosquitoes. Initial live weight did not have an effecton flight ability. Up to 75 percent of a mosquito' s preflight( live) weight was lost during exhaustive flight. Thereseemed to be a threshold below which weight loss did not occur. Virgin, gravid, and parous mosquitoes exhibiteddifferent tethered flight abilities. Uniparous and biparous mosquitoes did not fly as far as virgin or gravidmosquitoes.

studies have provided limited information on theINTRODUCTION distribution of Ae. triseriatus within wood lots. Such

studies have contributed very little information on theNumerous studies have examined the dispersal of flight ability of this important vector mosquito. This

Aedes triseriatus ( Say), particularly in relation to wood study examined the ability of virgin, gravid, and parouslots. Dispersal flight by Ae. triseriatus of 50- 100 m or Ae. triseriatus to fly under controlled, laboratorymore from isolated wood lots into or across open terrain conditions using a flight-mill system similar to thathave been reported in four separate studies in Wisconsin described by Rowley et al.( 1968) and interfaced with aDeFoliart and Lisitza 1980, Garry and DeFoliart 1975, microcomputer ( Clarke et al. 1984).

School et al. 1979, Mather and DeFoliart 1984). Schoolet al. ( 1979) recovered a marked female mosquito in a MATERIALS AND METHODSseparate wood lot 425 m from the wood lot in which itwas released. Sinsko and Craig ( 1979) found no Mosquito Rearing Procedures.evidence of interchange between two wood lots Aedes triseriatus eggs from a 3- years-oldseparated by 300 m of open terrain. However, Nasci laboratory colony were hatched in deoxygenated water,1982) suggested that fence rows connecting two wood and larvae were reared in white enamel 25 x 41 x 7 cm

lots functioned as corridors for movement between rearing trays ( 250 larvae per tray). Larvae were fed awood lots. He indicated that Ae. triseriatus flies mixture of ground Tetramin® and dog biscuits.extensively in search of oviposition sites and is not Pupae were harvested on developmental day 10,limited to wood lots. Beier and Tipis ( 1981) also and females were separated from males on the basis ofsuggested that Ae. triseriatus was not strictly confined size. Female pupae were divided into lots of 45 andto the forest and that the extent of dispersal may depend placed in 0.5 1 paper cans. Adult mosquitoes wereon the size and structure of a wood lot as well as on afforded access to cotton pads soaked in 0.3 M sucrose.peripheral areas. Berry and Craig ( 1984) found that Both adult and immature mosquitoes were maintainedrecently discarded tires in open terrain were readily at 25.6± 1° C and 75± 5 percent R.H. on a 16:8 light/colonized by Ae. triseriatus. Although this species dark cycle.seems to be somewhat reluctant to leave wood lots,increasing evidence suggests that it does fly across open Flight of Virgin Females.terrain under some circumstances. A single carton of 45 virgin female mosquitoes was

Oviposition traps and mark-release-recapture randomly selected for flight studies each day during a 6-

Journal Paper J- 12346 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project2277.

2Department of Entomology, Iowa State University, Ames, Iowa 50011, U.SA.Present Address: Clarke Outdoor Spraying Co., P. O. Box 72288, Roselle, IL 60172, U.S.A.

506 BULL SOC VECTOR ECOL DECEMBER, 1987

weeks period. Twelve individual mosquitoes were mosquitoes averaged 5,805 m( 36% flew less than 4,000

removed from this carton, inactivated by chilling, m, and 15% flew 9,000 m or more). In week 2( days 8-

weighted, and flown to exhaustion each day for six 12 PE), Ae. triseriatus females flew an average of

weeks. Mosquitoes that did not fly a minimum of 9,552.3 m. Forty-one percent flew more than 9,000 m1, 600 m in their initial flights were rejected as non- during this week, and 5 mosquitoes flew more thanfliers. 19,000 m. During week 3 ( days 15- 19), the mean

Nonfliers were replaced with other mosquitoes distance flown was 9,910 m. One 3- weeks-old

from the same carton. After exhaustive flight, mosquito flew 25,460 m and a second mosquito flew

mosquitoes were reweighed to determine weight loss 22,212 m. During week 3, 50 percent of the mosquitoes

during flight flew more than 9,000 m. A decline in flight abilityoccurred in the fourth week. The mean distance flown

Flight of Blood- fed Virgin Females. was 6,739 m, a decline of 32 percent from week 3. Flight

Unmated Ae. triseriatus females were blood-fed on performance remained near this level through week 6.

day 5 postemergence ( PE). Twelve blood-fed mos- The duration of sustained, exhaustive flights

quitoes were flown for a 24-hour period on days 0-4 during week 1 was 268 minutes. By week 3, the

postfeeding ( days 5- 9 PE). duration of sustained flights almost doubled to 478minutes or just under 8 hours. The length of flights

Flight of Parous Females. decreased considerably during weeks 4 and 5. As

Six-days-old (PE) females were mated by induced expected, there was a correlation between how far

copulation and held without sucrose for 24 hours before mosquitoes flew and the lengths of their flights.

being fed on a restrained rabbit. Individual engorged Mosquitoes flew at speeds between 24 and 31 ni/

mosquitoes were placed in 0.5 1 cartons with an minute during the first 35 days of this study. Duringoviposition cup ( Mather and DeFoliart 1983) and a week 6, mosquitoes flew only half as fast as in week 5.balsa ovistrip( Novak and Peloquin 1981). After blood- The correlation between how far mosquitoes flew and

feeding, mosquitoes were provided continuous access their flight speeds was low, and there was a negative

to 03 M sucrose in cotton pads. correlation between the length of flights and the average

On days 10- 12, after the initial blood meal( 17- 19 speeds of individual flights.

days PE), individual porous and virgin mosquitoes were The average weight of Ae. triseriatus flown in

flown for 24 hours. Another nonflown group of parous these experiments was 4.6 mg. Figure 2 shows the meanmosquitoes was given a second blood meal and allowed live weights of mosquitoes and the amount of weight

to oviposit. These biparous and similarly aged virgin loss during exhaustive flights. There seems to be a

mosquitoes were flown for 24 hours on days 20-22 after threshold below which weight loss does not occur.

the initial blood meal ( 27-29 PE). After flight weights were remarkably similar, with mostmosquitoes increased slightly as they aged. One-week-

Statistical Analysis. old mosquitoes weighed 4.06 mg, whereas, 6-weeks-Analysis of variance was used to test transformed old mosquitoes weighed 5. 15 mg. The weight of an

data ( log [ n + 1]), and correlation coefficients were individual mosquito did not affect how far it flew.

calculated to assess relationships between variables.

Priori comparisons were executed to test differences in Flight of Parous Female Mosquitoes.

flight performance between weeks. Statistically significant differences occurred in thedistance flown and duration of flight of virgin, parous,

RESULTS and biparous mosquitoes. Parous mosquitoes were 17-19 days old( PE), and biparous mosquitoes were 27-29

Flight of Virgin Female Mosquitoes. days old( PE)( TABLE 1). Virgin mosquitoes averaged

Statistically significant differences ( P < 0.001) 11, 717 m. Uniparous and biparous mosquitoes flew an

occurred in the distance flown, the duration, and the average of 7,734 m and 7,355 m, respectively. In thisspeed of flight of virgin Ae. triseriatus from one week study, virgin females flew 55.7 percent farther thanto another. However, differences were not evident for parous mosquitoes. Virgin females also flew longer

any of the flight parameters between days within weeks. ( 905 minutes) than either uniparous or biparous

Figure 1 shows the mean distance flown weekly by 40 mosquitoes ( 599 and 563 minutes, respectively). The

mosquitoes. A total of 416 mosquitoes was flown mean number of eggs laid by uniparous mosquitoes

during this study, of which 264 ( 63%) flew more than was 90. Biparous mosquitoes laid an average of 72

1, 600 m and were treated as fliers. During week 1, eggs.

DECEMBER, 1987 BULL SOC. VECTOR ECOL 507

DISCUSSIONextent of its flight ability. Aedes triseriatus flew wellfor the entire 6 weeks tested; however, there was aGenerally, Ae. triseriatus is considered to be ancharacteristic decline in flight ability beginning in theextremely limited flier, more or less restricted to wood fourth week. A similar decline has been observed inlots( its natural habitat). These studies indicate that Ae. other species of mosquitoes. Age-related changes in

triseriatus is a strong flier capable of flying much farther flight performance of virgin mosquitoes have beenthan the 50 to 100 m generally considered to be the reported by Rowley and Graham ( 1968), Rowley

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Figure 1. Mean distances flown by virgin female Aedes triseriatus mosquitoes. Sixty mosquitoes were flowneach week for 6 weeks.

508 BULL SOC. VECTOR ECOL DECEMBER, 1987

1970), and Nayar and Sauerman ( 1972, 1973). decrease in flight ability, but it did not occur until theMaximal flight performance in Aedes aegypti ( L.) and fourth week of adult life.

Culex tarsalis Coquillett occurred during the first 14 Rowley ( 1970) found that gravid Cx. tarsalis

days of adult life (Rowley and Graham 1968, Rowley mosquitoes flew substantially farther than virgins, but1970). Three-weeks-old Cx. tarsalis and Ae. aegypti did not find an age-related loss of flight ability in gravidflew only about 60 percent as far as younger( 1- 2 weeks- mosquitoes. For some reason, the physiological

old) mosquitoes. Aedes triseriatus had a similar changes that occur during the gonotrophic cycle allow

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Figure 2. Weekly preflight weights and weight lost during exhaustive flight by virgin female Aedestriseriatus mosquitoes.

DECEMBER, 1987 BULL SOC. VECIUR ECOL 509

Cx. tarsalis to maintain its ability to fly long distances. tires, are colonized by Ae. triseriatus emigrating fromLea( 1975) and Klowden and Lea( 1979) concluded that wood lots, and transovarial transmission of LAC viruschanges in mosquito activity during the gonotrophic to progeny provides an immediate focus of infectioncycle are under endocrine control mediated by the near human habitation ( DeFoliart and Lisitza 1980,neurosectretory system and the ovaries. Jones and Mather and DeFoliart 1984). In a retrospective studyGubbins ( 1978), Jones ( 1981), and Clarke and Rowley in Ohio, approximately half of the 71 LAC encepha-unpublished data) all found increased levels of lids cases examined from 1979 to 1981 were associated

spontaneous flight activity in gravid mosquitoes. Beier with old tires ( Craig 1983). Fourteen isolates of LACet al. ( 1982) did not fmd a correlation between the virus were obtained from 4,903 Ae. triseriatus larvaedistribution of eggs collected from ovitraps and the taken from a discarded tire in the back yard of a sickhorizontal resting distribution of marked or natural child' s home( Craig 1983). Leiser( 1981) demonstratedpopulations of Ae. triseriatus. They suggested that the magnitude of the urban distribution ofAe. triseriatusAe. triseriatus flies out of resting areas in search of when she found that 34 of 48 sections ( 66%) of Southoviposition sites to ensure efficient use of tree hole Bend, Indiana had positive ovitraps.resources throughout the forest. Undoubtedly, this The flight ability of this species, particularly insearch for oviposition sites would also result in urban environments, may be substantially greater thansome dispersal out of wood lots. Beier and Trpis the literature suggests. The ability of Ae. triseriatus to1981) and Nasci ( 1982) suggest that variation in fly significant distances probably plays a role in the

habitat may influence dispersal. Assuming that Ae. epidemiology of LAC virus and is significant in thetriseriatus does not undergo migratory flights, the ability of Ae. triseriatus to colonize discarded tires inappetential stimulus associated with being gravid both rural and urban environments. The natural flightcombined with limited oviposition sites, probably range of this mosquito needs to be evaluated along withrepresents a primary dispersal mechanism for this the influence that infection with LAC virus has on itsmosquito. flight ability.

The ability of Ae. triseriatus to disperse is These studies have demonstrated that Ae.important because a majority of La Crosse ( LAC) triseriatus has the ability to fly substantial distancesencephalitis cases occur in urban or rural environments. and for considerable lengths of time. It is not knownOften these areas are well removed from large wood if such flights occur under natural conditions; andlots considered to be the natural habitat of Ae. if they do, what factors or conditions mediate suchtriseriatus. Man-made containers, especially discarded flights. Additional studies, especially in the field,

TABLE 1. Mean distance( m), duration( min), and speed( m/min) flown by gravid, virgin, uniparous,and biparous Aedes triseriatus mosquitoes in a 24-hour period.

Pari ty N Distance ( SEM)' Duration ( SEM) Speed(SEM)

Gravid' 60 10780 ( 442) 763 ( 36) 14 ( 0.5)

Uniparous 15 7734 ( 789) 599 ( 93) 13 ( 1. 4)

Biparous 12 7355 ( 1258) 563 ( 112) 13 ( 1. 0)

Virgins 27 11717 ( 773) 905 ( 61) 13 ( 0.8)

Standard emir of the mean.

Gravid mosquitoes were 0-4 days old ( post-blood meal) and 5- 9 days old ( postemergence).

Virgin mosquitoes represent two groups 15- 17 days old flown as controls with the uniparousmosquitoes and 20-22 days old flown with the biparous mosquitoes.


and designed to determine how this species flies in inhibition of host-seeking in Aedes aegypti duringurban environments, are needed to evaluate the role oocyte maturation. J. Insect Physiol. 25: 231- 235.

of Ae, triseriatus as an urban vector of LAC virus.Lea, A. 0. 1975. The control of reproduction by a blood

REFERENCES CITED meal: the mosquito or a model for vector

endocrinology. Acta Trop. 32: 112-115.Beier, J. C. and M. Trpis. 1981. Local distribution of

Aedes triseriatus ( Diptera Culicidae) at the Leiser, L. 1981. Distribution of Aedes triseriatus ( Say)

Baltimore Zoo. Mosq. News 41: 447-455. in an urban area: Comparison of two surveymethods. Proc. Indiana Acad. Sci. 90: 248-253.

Beier, J. C., W. J. Berry, and G. B. Craig, r. 1982.

Horizontal distribution of adult Aedes triseriatus Mather, T. N. and G. R. DeFoliart. 1983. Effect of host

Diptera: Culicidae) in relation to habitat structure, blood source on the gonotropic cycle of Aedes

oviposition, and other mosquito species. J. Med. triseriatus. Am. J. Trop. Med. Hyg. 32: 189-Entomol. 19: 239-247. 193.

Berry, W. J. and G. B. Craig, Jr. 1984. Bionomics of Mather, T. N. and G. R. DeFoliart. 1984. Dispersion of

Aeries atropalpus breeding in scrap tires in gravid Aedes triseriatus ( Diptera Culicidae) from

northern Indiana. Mosq. News 44: 476-484. wood lots into open terrain. J. Med. Entomol. 4:384- 391.

Clarke, J. L., III, W. A. Rowley, S. Christiansen, and D.W. Jacobson. 1984. Microcomputer-based Nasci, R. S. 1982. Activity of gravid Aedes triseriatusmonitoring and data acquisition system for a in wooded fence rows. Mosq. News 42: 408-mosquito flight mill. Ann. Entomol. Soc. Am. 77: 412.

119- 122.Nayar, J. K. and D. M. Sauerman, Jr. 1972. Flight

Craig, G. B., Jr. 1983. Biology of Aedes triseriatus: performance and fuel utilization as a function of

Some factors affecting control. Pp. 329-241 In age in female Aedes taeniorhynchus. J. Israel

California Serogroup Viruses ( C. H. Calisher and Entomol. 7: 27- 35.

W. H. Thompson, eds.). Alan R. Liss, Inc., New

York, NY, 399 pp. Nayar, J. K. and D. M. Sauerman, Jr. 1973. A

comparative study of flight performance and fuelDeFoliart, G. R. and M. A. Lisitza. 1980. Activity by utilization as a function of age in females of Florida

Aedes triseriatus in open terrain. Mosq. News 40: mosquitoes. J. Insect Physiol. 19: 1977- 1988.

650-652.Novak, R. J. and J. J. Peloquin. 1981. A substrate

Gary C. E. and G. R. DeFoliart. 1975. The effect of modification for the oviposition trap used forbasal treehole closure on suppression of Aedes detecting the presence of Aedes triseriatus. Mosq.triseriatus ( Diptera Culicidae). Mosq. News 35: News 41: 180- 181.

289- 297.Rowley, W. A. 1970. Laboratory flight ability of the

Jones, M. D. R. 1981. The programming of circadian mosquito, Culex tarsalis Coq. J. Med. Entomol. 7:flight activity in relation to mating and the 713-716.

gonotropic cycle in the mosquito, Aedes aegypti.

Physiol. Entomol. 6: 307- 313. Rowley, W. A. and C. L. Graham. 1968. The effect ofage on the flight performance of female Aedes

Jones, M.D. R. and S. J. Gubbins. 1978. Changes in the aegypti mosquitoes. J. Insect Physiol. 4: 719-729.

circadian flight activity of the mosquito Anophelesgambiae in relation to insemination, feeding and Rowley, W. A., C. L. Graham, and R. E. Williams.oviposition. Physiol. Entomol. 3: 213- 220. 1968. A flight mill system for the laboratory study

of mosquito flight. Ann. Entomol. Soc. Am. 61:

Klowden, M. J. and A. 0. Lea. 1979. Humoral 1507- 1514.

i

DECEMBER, 1987 BULL SOC VECTOR ECOL 511

Scholl, P. J., C. H. Porter, and G. R. DeFoliart. 1979. Sinsko, M. J. and G. B. Craig, Jr. 1979. Dynamics ofAedes triseriatus: persistence of nulliparous an isolated population of Aedes triseriatusfemales under field conditions. Mosq. News 39: Diptera: Culicidae). 1. Population size. J. Med.368- 371. Entomol. 15: 89-98.

BULL SOC. VECtOR ECOL, 12(2 ): 512-516 DECEMBER, 1987

THE Ell-,ECT OF IMMATURE MOSQUITOES ON OVIPOSITION BY

CULEX PIPIENS QUINQUEFASCIATUS AND CULISETA INCIDENS

DIPTERA: CULICIDAE) IN THE NIELD1

T. R. Wilmot2' 3, S. E. Cope2, and A. R. Bang

ABSTRACT: A study was conducted of oviposition preferences of Culex pipiens quinquefasciatus Say and Culisetaincidens ( Thomson) females among field containers with immature Cx. p. quinquefasciatus, Cs. incidens, bothspecies together, or with no immatures. Females of both species oviposited preferentially in containers with con-specific immatures but other unidentified factors seem to be equally or more important in oviposition site selection.

INTRODUCTION Marks by Gubler( 1971) and Aedes sierrensis ( Ludlow)by Ahmandi and MacClelland ( 1983). Oviposition

All mosquito species have a characteristic, more or attraction could not be shown for eggs of Aedesless restricted, habitat in which their larvae develop. It triseriatus by Bentley et al. ( 1976).seems likely that specific ovipositional preferences of With very few exceptions, these experiments wereadult mosquitoes are most responsible for this conducted under controlled laboratory conditions anddistribution of immatures. Physical and chemical the influence of immature mosquitoes on oviposition infactors possibly affecting the attraction of mosquito the field is not known. The present paper reports thespecies of oviposition sites have been the subject of effects of the presence of immatures on oviposition ofnumerous investigations. Culex pipiens quinquefasciatus Say and Culiseta

Pheromones or other chemicals associated with the incidens ( Thomson) in the field.

presence of immature mosquitoes may possiblyinfluence oviposition. The presence of attractive METHODS AND MATERIALS

substances has been associated with larvae of Culexpipiens by Ikeshoji( 1966), Aedes aegypti Linnaeus by Experiments were conducted in an abandoned and

Soman and Rueben( 1970) and Roberts and Hsi( 1977), undisturbed experimental orchard on the campus of the

Aedes atropalpus ( Coquillett) by Kalpage and Brust University of California, Los Angeles. Ovitrap con-1973) and Maire( 1984, 1985), Aedes triseriatus Say by tainers were constructed that measured approximately

Bentley et al.( 1976) and McDaniel et al. ( 1976), Culex 34 x 34 x 15 cm and consisted of a sheet of plastic

tritaeniorhynchus Giles and Anopheles stephensi supported by 4 interlocking wooden side pieces. The

Liston by Reisen and Siddiqui ( 1978), and Aedes containers were maintained in locations shaded and

communis DeGeer by Maire and Langis( 1985). Maire protected by avocado tree branches. Mosquito larvae

and Langis( 1985) showed that Ae. communis females used in all experiments were from eggs collected at the

were attracted to factors associated with larvae of Ae. study site. Samples of larvae from several egg raftsatropalpus as well as those of Ae. communis. Pupae were reared in the laboratory to confirm identifications;associated factors have been shown with Ae. atropalpus all were Cx. p. quinquefasciatus or Cs. incidens andby Kalpage and Brust( 1973), Ae. aegypti by Roberts separation of the two species was completely reliable.

and Hsi ( 1977), and Culex salinarius Coquillett by Nine containers were set at the study site on 13 JulyAndreadis ( 1977). 1982 and filled with tap water to which dry dog food and

Oviposition attractants may not be universal. rabbit chow was added. On 14 July, 50 to 1000 newlyLarval rearing water was unsuccessfully tested for hatched larvae ( Cs. incidens, Cx. p. quinquefasciatus ,attraction to Aedes albopictus and Aedes polynesiensis or both species together) were added to eight containers;

This work was supported by Research Grant No. USPHS AI-11847 from the National Institutes of Health, Bethesda,Maryland.

2School of Public Health, University of California, Los Angeles, California 90024, U.S.A.3Present address: Midland County Mosquito Control, 2957 Venture Drive, Midland, Michigan 48640-8906, U.S A.

DECEMBER, 1987 BULL SOC. VECTOR ECOL513

one container had no larvae. The populations of larvae ( TABLE 1). In two of three trials most Cs. incidens eggwere assigned to the various containers by using rafts were collected in containers with only conspecificrandom numbers. Larvae were allowed to develop and larvae and more were collected in containers with bothpupae were removed from the containers before species than in those with Cx. p. quinquefasciatus onlyemergence. Egg rafts were identified and removed or with no larvae ( TABLE 2). The attractancy ofdaily. Tap water was added as needed to maintain the breeding water to females was possibly reduced bywater level at approximately 12 cm, but no organic crowding of larvae. Containers to which 1000 larvaematter was added by the investigators after the first day. were added collected fewer egg rafts than containersThe containers were examined daily until all larvae had with 50 or 500 larvae.pupated or died ( 3 August). The experiment was Analysis of variance (TABLES 3 and 4) suggestsrepeated from 4 August to 26 September and again from that oviposition by both species is influenced by27 September to 9 November. Between trials the con- immature mosquitoes in the containers. Analysis oftainers were cleaned and refilled and the numbers of variance and graph of the numbers of egg rafts per weeklarvae to be added were again assigned randomly. hi the ( Figure 1) suggest, however, that other factors alsosecond and third trials 12 and 14 containers, influence oviposition. The reduction in egg raftsrespectively, were used and only rabbit chow was added collected after three or four weeks suggests a change into each container.

attractancy with time. Factors possibly associated withthis change include age of infusion ( Kramer and Mulla

RESULTS 1979), succession of algal species or deterioration ofpheromones. The decline in numbers of egg rafts

Most Cx. p. quinquefasciatus egg rafts were collected after the first trial could have been due to ancollected in containers with only conspecific larvae actual decline in the number of ovipositing females in

TABLE 1. Number of Culex pipiens quinquefasciatus egg rafts collected from field containers during threetrials.

Number of larvae added to container

Cs. 50 500 1000 0 0 0 50 450 50 950 0 0 0 0Trial Cx. 0 0 0 50 500 1000 450 50 950 50 0 0 0 0 Total

I 138 119 81 127 129 121 162 132 - - 77 - - - 1086II 59 66 40 103 127 71 61 49 53 53 68 89 - - 839

III 66 34 10 79 71 66 77 48 58 23 50 42 68 32 724

Total 263 219 131 309 327 258 300 229 111 76 195 131 68 32 2649

TABLE 2. Number of Culiseta incidens egg rafts collected from field containers during three trials.

Number of larvae added to container

Cs. 50 500 1000 0 0 0 50 450 50 950 0 0 0 0Trial Cx. 0 0 0 50 500 1000 450 50 950 50 0 0 0 0 Total

I 43 48 25 29 22 16 19 39 - - 27 - - - 268II 16 20 18 19 37 27 24 17 18 19 15 25 - - 255

III 16 15 4 10 4 5 6 5 13 5 10 1 9 7 110

Total 75 83 47 58 63 48 49 61 31 24 52 26 9 7 633


TABLE 3. Analysisl of Culex pipiens quinquefasciatus oviposition.

Source DF SS MS F P

Trial 2 23354. 51 11677.26 122.81 0.01

Week 7 9295.94 1327.99 13.97 0.01

Mosquito 3 846.14 282.05 2.97 0.05

Error 194 18446.48 95.09

Total 206 51943.47

1General linear models procedure.

TABLE 4. Analysisl of Culiseta incidens oviposition.

Source DF SS MS F P

Trial 2 2363.93 1181.97 96.41 0.01

Week 7 382.65 54.66 4.46 0.01

Mosquito 3 198.38 66. 13 5.39 0.01

Error 194 2378.51 12.26

Total 206 5323.48

1General linear models procedure.

the area or to a change in the attractancy of the Traps for the collection of gravid Culex

containers. Populations of Culiseta species in mosquitoes are now used in arbovirus surveillance

California typically are greater in cooler months( Miura programs ( Reiter et al. 1986) and ovitraps are used as

et al. 1976); a decline in number of Cs. incidens in the part of a program to control Ae. triseriatus and

fall is unexpected. The greater amount of organic LaCrosse encephalitis in LaCrosse County, Wisconsinmatter added to the containers in the first trial pro- ( Parry 1983). Measures of oviposition am under

bably contributed to the more rapid development of investigation as a means of monitoring populations oflarvae and may have been responsible in part for several mosquito species. Further investigations of

the greater number of egg rafts collected during that the factors influencing mosquito oviposition and

trial, their relative importance in the field may lead to anincreased use of female or egg collections in the study

DISCUSSION of mosquito biology and control. Further under-

standing of the effect of immature mosquitoes on ovi-A clear understanding of the factors influencing the position may benefit the development of models of

oviposition behavior of mosquitoes has not yet been mosquito population dynamics.

developed. Conspecific immatures may attract gravidfemales but other unidentified factors, which influence Acknowledgements

the quality of the environment for larval development,may be equally or more important in oviposition site We thank Dr. Charles Taylor, Department of

selection in the field. Large numbers of larvae may Biology, University of California, Los Angeles, for hisrender a site less attractive to females. helpful comments.


480 —

l;.a _ 120

I.I.

Culex 100

360 —

rCuliseta

80

x240 — ei

60

II 40

120 — • II 20

I I I ancn

1 2 3

aoao aoaA wW

240— c

V1

V 40

O 120— pL

ti 20 N

ZI I I I I I I I

0 Z

1 2 3 4 5 6 7 8

240—C

N

40

120— e4•

20

0I I I I I I

0

1 2 3 4 5 6

Collection Week

Figure 1. Weekly totals of egg rafts collected in field containers during three trials. ( a) 13 July to 3August, ( b) 4 August to 26 September, and ( c) 27 September to 9 November.


REFERENCES CITED Make, A. and R. Langis. 1985. Oviposition responsesof Aedes ( Ochlerotatus) communis ( Diptera:

Ahmandi, A. and G. A. H. MacClelland. 1983. Culicidae) to larval holding water. J. Med.

Oviposition attractant of the western tree hole Entomol. 22( 1): 111- 112.

mosquito, Aedes sierrensis. Mosq. News 43(3):343- 345. McDaniel, I. N., M. D. Bentley, H. P. Lee, and M.

Yatagai. 1976. Effects of color and larval

Andreadis, T. G. 1977. An ovipositional attractant of produced attractants on oviposition by Aedespupal origin in Culex salinarius. Mosq. News triseriatus. Env. Entomol. 5(3): 553-556.

37( 1): 53- 56.Miura, T., J. W. Kleiwer, and C. H. Tempelis. 1976.

Bentley, M.D., I. N. McDaniel, H. P. Lee, B. Stiehl, and Seasonal occurrence of Culiseta incidens in

M. Yatagai. 1976. Studies of Aedes triseriatus foothills of Fresno County, California. Mosq.oviposition attractants produced by Aedes News 36( 3): 343-349.

triseriatus and Aedes atropalpus ( Diptera:

Culicidae). J. Med. Entomol. 13( 1): 112- 115. Parry, J. E. 1983. Control of Aedes triseriatus in

LaCrosse, Wisconsin. Pp. 355-363, In CaliforniaGubler, D. G. 1971. Studies on the comparative ovi- Serogroup Viruses. ( C. H. Calisher and W. H.

position behavior of Aedes albopictus and Aedes Thompson, eds.). Alan R. Liss, Inc., New York.

polynesiensis. J. Med. Entomol. 8( 6): 675-682.Reisen, W. K. and T. F. Siddiqui. 1978. The influence

Ikeshoji, T. 1966. Studies on mosquito attractants and of conspecific immatures on the oviposition

stimulants. Part I. Chemical factors determining preferences of the mosquitoes Anopheles stephensi

the choice of oviposition site by Culex pipiens and Culex tritaeniorhynchus. Pakistan J. Zool.

fatigans and pallens. Japan J. Exp. Med. 36( 1): 49- 10( 1): 31- 41.

59.

Reiter,P., W.L.Jakob, D. B. Francy, and J. B. Mullenix.Kalpage, K. S. P. and R. A. Brust 1973. Oviposition 1986. Evaluation of the CDC gravid trap for the

attractant produced by immature Aedes atropalpus. surveillance of St Louis Encephalitis vectors in

Env. Entomol. 2(4): 729-730. Memphis, Tennessee. J. Am. Mosq. Cont Assoc.2(2): 209-211.

Kramer, W. L. and M. S. Mulla. 1979. Oviposition

attractants and repellents of mosquitoes: Roberts, D. R. and B. P. Hsi. 1977. A method for

oviposition responses of Culex mosquitoes to evaluating ovipositional attractants for Aedesorganic infusions. Env. Entomol. 8(6): 1111- 1117. aegypti ( Diptera Culicidae) with preliminary

results. J. Med. EntomoL 14( 1): 129- 131.

Maim, D. J. 1984. An analysis of the oviposition

responses of Aedes atropalpus to experimental Soman, R. S. and R. Rueben. 1970. Studies on the

oviposition waters. Mosq. News 44(3): 325- 329. preference shown by ovipositing females ofAedes aegypti for water containing immatures of

Maire, D. J. 1985. Effect of axenic larvae on the the same species. J. Med. Entomol. 7(4): 485-

oviposition site selection of Aedes atropalpus. J. 489.

Am. Mosq. Cont. Assoc. 1( 3): 320-323.

BULL SOC. VECTOR ECOL, 12(2): 517-527 DECEMBER, 1987

PA'FIERN OF THELYTOKY ACQUISITION IN MUSCIDIFURAX RAPTOR

GIRAULT AND SANDERS ( HYMENOPTERA: PTEROMALIDAE)

E. F. Legnerl

ABSTRACT: The manner in which uniparental ( thelytokous) reproduction is incorporated in a hybrid biparentalarrhenotokous) population of Muscidifurax raptor Girault and Sanders after mating with males of thelytokous

Muscidifurax uniraptor Kogan and Legner implicates extranuclear factors; e.g., microorganisms and chemicalsubstances. Genetic change may not be involved in the acquisition of thelytoky.

INTRODUCTION subsequently produced thelytokous F offspringLegner 1987a). The present study details the

Increasing attention is focused on the importance reproductive changes observed during the acquisitionof hymenopterous parasitoids in the natural control of phase of thelytokous reproduction.

synanthropic flies as costs and hazards of chemicalcontrol mount ( Morgan 1981, Mullens et al. 1986, MATERIALS AND METHODSPetersen and Meyer 1983, Rutz and Axtell 1979). When

introducing parasitoid strains with attributes that afford To study the pattern of acquisition of thelytokousa greater potential for fly control( Legner et al. 1982), it reproduction, separate cohorts each of 10- 18 3-day-oldis theoretically advantageous to reduce outbreeding females of M. uniraptor from Cayey, Puerto Rico, andwith local populations in order to slow the loss or Israel and Utah strains of M. raptor were isolated indilution of desired characteristics. The adoption of a screened polystyrene vials (46 cm'), with a basal area

completely parthenogenetic ( thelytokous) reproductive of 7 cmz Cultures which originated from> 100 femalesmode in the preferred strain may minimize the loss of each captured in the wild had been maintained for onlysuch genes that confer the desired traits because 2-3 generations to minimize inbreeding ( Legner 1979).outbreeding is reduced or eliminated. They were mated for one day to <_1- day old males

A thelytokous species, Muscidifurax uniraptor secured at random. Each female was supplied dailyKogan and Legner, from Cayey, Puerto Rico, was found with 20, 24 to 30-h-old puparia of Musca domestica L.to produce naturally an unusually high number of males ( 6.4 ± 0.5 mm X 2.8± 0.2 mm), distributed randomlyearly in its reproductive period ( Legner 1985a), over the vial base. Flies were reared to pupation usingwhereas, exposure of the developing ova to high commercial CSMA®medium.

temperatures previously was required to induce male Host puparia were exposed to parasitoids for 24-h

offspring ( Legner 1985b). Although the role of such at 25.5± 1° C, 55% RH, and a 13L:11D photoperiod ofmales remains obscure, they are known to be functional ca. 269 lux irradiance at table level. Light was suppliedin the thelytokous Aphytis mytilaspidis ( LeBaron) by fluorescent lamps. Parasitization efficiency at thisRossler and DeBach 1972). host density and in this environment was near optimum

These naturally produced males of M. uniraptor ( Legner 1967, 1979). Puparia were then incubatedseemed like ideal candidates for testing whether separately in gelatin capsules ( 10 X 25 mm) for thethelytoky could be inherited in arrhenotokous emergence of F, parasitoid and host progeny.Muscidifurax raptor Girault and Sanders, especially as Unemerged puparia were dissected to detect abortedthe former occupies an intermediate position parasitism.

taxonomically ( Kogan and Legner 1970) and Parasitoid longevity, male and female progeny,alleleomorphically ( Kawooya 1983) in the genus. and host destruction were recorded for each female

Thelytoky was then transferred by mating the M. through the age of 16 days, which is about half the lifeuniraptor males to hybrid females of M. raptor created expectancy in the described environment ( Legnerby crossing strains that were secured from 1987a, Legner and Gerling 1967). The importance of

geographically distant areas ( Legner 1987a). In the extended experimental time for viewing behavior accu-transfer process, a change in reproductive behavior was rately is becoming recognized for parasitoids ( Hey andobserved by the mated hybrid females which Gargiulo 1985) and Drosophila spp. (Templeton 1982).

Department of Entomology, University of California, Riverside, CA 92521 U.SA.


Modified reproductive potential statistics for used to begin the 1,. calculation. The statistic mxlaboratory studies involving parasitoids were derived as measured the " effective" number of female offspringdiscussed previously ( Legner 1985a, 1987a). These per female in the age interval x( 24-h), as only emergedincluded derivations of the Birch( 1948) formula for the offspring were counted. This arrangement permitted

net reproductive rate ( R0) and intrinsic rate of natural comparisons of adult parasitoid behavior, and

increase ( rm); the net parasitization rate ( Rp) and eliminated slight strainal differences inherent amongintrinsic rate of parasitization( r„); the net total fecundity developmental stages. Dissections of unemerged

rate( males+ females) ( Ri) and intrinsic total fecundity puparia revealed < 2 percent aborted parasitism, which

rate( r,); and net host destruction rate( Rd) and intrinsic gave credibility to adult parasitoid emergence data.rate of host destruction ( rd). Such statistics enable Experiments were conducted with replicates

comparisons of the direct effects of mating on female arranged in a completely random split plot design inparasitoids. space. Analyses of variance were performed on the

In deriving these values, the pivotal age, or time for binomial data transformed to iX+ 1/ 2, and significant

development from the egg to adult emergence, was differences tested with Duncan' s multiple range tests

estimated as the mean length of development of females ( Duncan 1955, Steel and Torrie 1960).

at 25.5± 1° C, 55% RH. Females, which were three days

old( post eclosion) when an exposure began, had a mean RESULTS AND DISCUSSION

pivotal age of 24.5 days. An estimated 90 percent

survival rate of immature females from oviposition was The pairing of( Israel females X Utah males) M.

TABLE 1. Female progeny, total progeny, and host destruction by P, and hybrid populations ofMuscidifurax raptor and Muscidifurax uniraptor, where oviposition is continuous at 25.5 ±

1° C. and 55% RH on 20 Musca domestica puparia daily for 14 days. 1

Avg. No./(s) Avg. HostPopulation Females Total Progeny Destruction/( s-)

Puerto Rico Females - virgin 26.0• 199.7ab 18.0•

3.4) 9.4) 0.43)

Israel Females - mated 842' 124.0' 13. 4b

10.7) 19. 1) 0.67)

Utah Females - mated 169.4d 204. 1a6 17. 2'

8. 5) 9.8) 0.47)

Israel Females w/ Utah Males 78.01' 94.5d 9.8'

18.6) 17.7) 1. 21)

Israel Females X Utah Males)Females 121. 5' 204.2ab 17.0'

w/ Puerto Rico Males 2. 1) 5. 1) 0.50)

Israel Females X Utah Males)Females 39.0' 219.0' 18. 7"

X Puerto Rico Males]Females - virgin 4. 8) 7. 9) 0.32)

Mean squared error ( 66 d02 2.999 3. 537 0.154

Values followed by the same letter are not significantly different( P<_0.05; Duncan' s [ 1955] multiple rangetest); analyses performed on transformed expressions of single females( X + 1/ 2).

On transformed scale.


raptor female hybrids with Puerto Rican M. uniraptor population through 25 generations as of this writing.males produced female progeny in every replicate. All Matings of male M. uniraptor with female hybrids fromof these progeny reproduced by thelytoky because the reciprocal cross ( Utah females X Israel males) didmating was not required for the subsequent production not yield female progeny, and thus were judgedof female offspring. Thelytoky was retained by this unsuccessful.

Muscidifurax uniraptor PUERTO RICO 1981-

P- I Virgin)TOTAL HOSTS

20 - KILLEDcr,..

0' ii.,O'•-

0- o-•.,`

Rd= 226.66v' •• .'t

t o--- 4. rd' 01911•16 - •••-

W \ 0.•0..

0O _ / TOTALr t

ZPROGENY s

r— Rt= 179.69rt =0.1833

8 -

4 -

0 1 1 1 1 1 1 1 1 1 1 1 1 1 1

l x100

220

r C7Z 11 R0. 23. 40 0. 75 ZW rm= 0.12910 16 dda: 1'

a•Z12 0.50

Z0

C.6 i H8 a:Q

00.25 a-

inxOtxa_

i

0 03 4 5 6 7 8 9 10 II 12 13 14 15 16

AGE OF ADULT FEMALE ( days)

Figure 1. Survival rate ( 1X), and daily fecundity ( m) (= female progeny), male progeny, total progenytx), and host destruction ( d,) for 10 virgin females of the Cayey, Puerto Rico strain of

Muscidifurax uniraptor, ovipositing continuously at 25.5± 1° C. and 55% RI-I. on 20 Musca

domestica puparia per day.


A distinctive reproductive pattern was evident Utah isolates, respectively. The fecundity of the Israelduring the transfer of thelytoky to the( Israel females X strain in the presence of Utah males is shown in Figure

Utah males) female hybrid as diagrammed in Figures 1- 4, and the( Israel females X Utah males) hybrid females

6. Original parental fecundities (= female progeny) are mated with M. uniraptor males in Figure 5. Fecundityshown in Figures 1- 3 for the Puerto Rico, Israel and of the thelytokous hybrid resulting from the latter cross

Muscidifurax raptor ISRAEL-( P- 1 )

20 -

o _ o

16 - i' .,• q TOTAL HOSTS

KILLED Rd= 160. 01O - d q• r d= 0.1817

5.

I`- • • i

e TOTAL" -' d

8 - PROGENY %.

AA

1r, -,.-4 - Rt= 111. 60 •

rf= 0.1705

o I I l I I I l I 1 1 4 I 1 1

I00

t•

20 -

rZ 0.752

O 16 - O j

R°= 75.78a-

rm= 0.1588O 12 - 0. 50 (Z Z

O

Q 8 - m.z

O0. 25a-

4 - 0

0 I i i I I I I I I I I I 1 03 4 5 6 7 8 9 1 0 1 1 2 1 3 1 4 1 5 1 6


Figure 2. Survival rate ( 1x), and daily fecundity ( m,) (= female progeny), male progeny, total progenyt,), and host destruction( dx) for 18 mated females of the Israel strain of Muscidifurax raptor,

ovipositing continuously at 25.5± 1° C. and 55% RH. on 20 Musca domestica puparia per

day.

DECEMBER, 1987 BULL SOC VECPOR ECOL 521

is shown in Figure 6. expressed largely during the last half of the ovipositionThe presence of the Utah male had no significant period ( Figure 4, TABLE 1). Microparasitoids also

affect on the fecundity of the Israel strain( Figures 2 and appeared, which were typically found in the Utah strain4, TABLE 1). However, there was a significant ( Figure 3). The resultant hybrid mated to M. uniraptorP93.05) reduction in total progeny and host destruction males, shown in Figure 5, resembled the Utah parent in

Muscidifurax raptor UTAH-( P- 1 )

TOTAL HOSTS

20 KILLED

1A r` 0.

Rd= 216. 6016 (. `% . TOTAL `

0. O._Qrd=

0. 1899

p PROGENY '"1

p._p.._0

12

Q Rt= 183.78`,

8rt = 0. 1858 0""

4

d'+? MICROS d MICROS0

I 00

20 - R°= 152. 46

r rm= 0. 1779 0

Z - 0.75 ZW

5

O 16 -

Ci 12 - 0.50

Z ZO_

8 -Q

O0.25 Q-

4 - •...• a. d cc

vr w. •

O i i t i i t i i t i t t i t 03 4 5 6 7 8 9 10 11 12 13 14 15 16


Figure 3. Survival rate( 1x), and daily fecundity ( m.) (= female progeny), male progeny, total progenyt), and host destruction( dx) for 10 mated females of the Utah strain of Muscidifurax raptor,

ovipositing continuously at 25.5± 1° C. and 55% RR on 20 Musca domestica puparia per

day.


total progeny production and host destruction, but had Pattern of this latter part of the reproductive period

a significantly reduced fecundity( P50.01) after the 9th corresponded closely to the first half of the reproductive

day of oviposition when high numbers of male progeny period of thelytokous M. uniraptor ( Figure 1).

were observed, accompanied by a rapid drop in the Data for the ensuing double hybrid ( Figure 6)output of female progeny ( Figure 5, TABLE 1). The correspond closely to that of the Puerto Rican parent

Muscidifurax raptor ISRAEL9 X UTAHd

20

16

TOTAL HOSTS

KILLED

2 ^, N. % R

O i • d !\ / '' "• Q Rd= 124. 0i rd= 0. 1752d TOTAL ..

w '

6PROGENY

Y 44 lF-+'`•

Rt= 85. 1

MICROS rt= 0. 1634

0

1. 00x

x4t

20—

r CD

Z 0.75 Zw

00 16-

cc cc

p 12- R0= 70.20.50

m xrm= 0. 1560

OU

O0.25 0_

O

4-0-

0t A...• I y...I

3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 60


Figure 4. Survival rate( 1x), and daily fecundity ( m.) (= female progeny), male progeny, total progeny

tx), and host destruction( dx) for 10 females of the Israel strain ofMuscidifurax raptor, matedwith random males of the Utah strain and ovipositing continuously at 25.5± 1° C. and 55%RH. on 20 Musca domestica puparia per day.


Figure 1), indicaring that the typical thelytokous form diagramed in Figure 5 reproduced by thelytoky,had been produced. Its character differed only in a regardless from which part of the oviposition cycle theycontinued production of some female offspring through emanated, as judged by the female progeny producedthe 15th day of oviposition and in the appearance of from tested virgin females.

micmparasitoids ( Figure 6). All female offspring Although such changes of progeny sex ratio to

Muscidifurax raptor M. uniraptor

ISRAEL9 X UTAH d,) X

20 TOTAL HOSTSKILLED p•

o.- o_o--Q Rd= 214. 7

o.-•°'3?

rd= 0. 189316 p...

w TOTAL \ 4•

Z1"

r-''•"% PROGENY -' r-'\ No.

12 Rt= 183. 8O

rt= 0. 1830 Q

8

4

Qg MICROS0

1. 00Qx

20 -c9

Z — 0.75 Z

016 -

Ro= 109.4cra_ - r

0.50

8 -

0.25

4 - 4

3 4 5 6 7 8 9 10 II 12 13 14 15 16


Figure 5. Survival rate ( 1x), and daily fecundity( m) (= female progeny), male progeny, total progeny

tx), and host destruction( d) for 10 hybrid ( Israel female X Utah male) female Muscidifuraxraptor mated with random Muscidifurax uniraptor males and ovipositing continuously at25.5± 1° C. and 55% RH. on 20 Musca domestica puparia per day.


favor males after mating with M. uniraptor males different anatomical types of sperm are known in this

Figure 5) may involve sperm depletion after the 9th species ( McCoy 1967), which may also differ inoviposition day ( Legner 1987a), this is not strongly fertilization capabilities.

suspected in the present case as spermathecae contained A second possibility considers the involvement ofviable sperm in all > 16 day old females. However, extranuclear factors in the induction of thelytoky as was

Muscidifurax raptor M. uniraptor

VIRGINISRAEL y X UTAH( 1) X d ]

TOTAL HOSTS KILLED20

yr4. 0

16d TOTAL

1 \• Rd

0? 914PROGENY d rd

s-- 1 •z

12 Rt= 197. 1C7 rt= 0. 1870 If

8

4

MICROS c( MICROS

0

1. 00x

20 - 1

z _ a. r

0.75 Z

O16 -

CC _ dd o:

p 12 - R0=35422Z m= z

0

0 p8 -

0.25 am

x 04 - a

0 03 4 5 6 7 8 9 10 II 12 13 14 15 16


Figure 6. Survival rate ( 1x), and daily fecundity ( mx) (= female progeny), male progeny, total progenyç), and host destruction ( dx) for 16 virgin double hybrid females , [( Israel females X Utah

males) females X Cayey malesifemales, ovipositing continuously at 25.5 ± 1° C. and 55%RR on 20 Musca domestica puparia per day.


shown with the inheritance of gregarious oviposition in The last two hypotheses preclude a genetic aspectMuscidifurax raptorellus Kogan and Legner ( Legner to the inheritance of thelytoky. If, for example,1986, 1987b). Extranuclear heredity is a well- microorganisms and their accompanying capacity todocumented phenomenon among primitive organisms produce chemicals or inducing enzymes are transferredBeale and Knowles 1978), and microorganisms are from the male' s seminal fluid into the chorion ( or

known to alter sex ratios in parasitoids by killing another part) of the next-to-be-oviposited ova, and frommales or females ( Krell and Stoltz 1979, Stoltz and here they influence endomitosis in the next generation,Vinson 1977, Stoltz et al. 1976, Vinson and Stoltz 1986, thelytoky would be passed on without genetic change.Werren et al. 1986), or by altering behavior in other With such a system, it is possible to envisionMetazoa ( Bull 1983). quantitative variation in microorganisms and enzymes

A third chemical legacy hypothesis assumes that at ( or other) and hence the number of thelytokous femalesinsemination females may receive certain chemicals produced. Because the titre appears to build up duringwhich modify reproduction. The finding that repro- host-free periods ( Legner 1985a, Legner and Gerlingduction is influenced in a way that depends on the nature 1967), microorganismal multiplication and/ or

of the male could be explained by a reproduction- elaboration of the chemical substance(s) would have to

modifying chemical from the male as well as by proceed relatively slowly.microorganisms. There is another aspect to thelytoky induction that

Chemical substances affect behavior of insects points to the probable specificity of any such micro-following mating. Reports include a lepidopteran organisms which may be involved. It was found thatWebster and Carde 1984), an ichneumon wasp thelytoky also could be fixed in a hybrid M. raptor

Venturia ( Nemeritis) canescens ( Gravenhorst) ( where population by backcrossing to one of the parental males,heneicosane was involved) (Mudd et al. 1982); and the but not to both( Legner 1987a). Thus, if each strain ordipteran Drosophila involving enzymes ( Mane et al. species of parasitoid harbored its own specific strain of1983, Richmond and Senior 1981). Prostaglandins, microorganism, only certain crosses of the latter mayderivatives of certain polyunsaturated fatty acids, alter yield a strain capable of affecting the endomitoticegg laying behavior in crickets( Stanley- Samuelson and process. Continued biochemical and microbiologicalLoher 1986). It has been suggested that an influence on investigations are expected to elucidate further thethe chemosensory responsiveness of an individual by pathways to inheritance of thelytoky.chemical cues derived from its parents would be hard to

distinguish from a genetic effect ( Corbet 1985). REFERENCES CITED

Whatever the agent for induction of thelytoky,there is an apparent relationship to the titre of the Beale, G. and J. Knowles. 1978. Extranuclear Genetics.causative factor. For example, production of Edward Arnold, London. 142 pp.thelytokous females in M. uniraptor is greatest when

oviposition is interrupted for 24 hours by scheduling Birch, L. C. 1948. The intrinsic rate of natural increasehost presentation on alternate days( Legner 1985a) or by of an insect population. J. Anim. Ecol. 17: 15- 26.

slowing oviposition rates during early adult life( Legnerand Gerling 1% 7). Such interferences may allow the Bull, J. J. 1983. Evolution of Sex Determiningtitre of the factor to rise. Higher concentrations of Mechanisms. The Benjamin/ Cummings Publ. Co.,microorganisms or chemicals may thus guarantee a Inc., Menlo Park, CA. 316 pp.greater proportion of thelytokous female offspring. It

could reasonably be assumed that both microorganisms Corbet, S. A. 1985. Insect chemosensory responses: aand certain chemicals that they produced are, involved, chemical legacy hypothesis. Ecol. Entomol. 10:

with the latter inducing endomitosis ( Legner 1985b) 143- 153.

which results in thelytokous offspring.Heat treatment ( 32.2°C. for> 24-h) beginning at a Duncan, D. B. 1955. Multiple range and multiple F

critical stage in oocyte formation blocks endomitosis tests. Biometrics 11: 1- 41.

and male progeny result ( Legner 1985b). If anymicroorganisms are involved directly or indirectly in Hey, J. and M. K. Gargiulo. 1985. Sex-ratio changes inpromoting endomitosis, the higher temperature may Leptopilina heterotoma in response to breeding. J.either kill or inactivate them. Earlier work ( Legner Heredity 76: 290-211.1985b) also would point to their probable residence in

oocytes which are in later developmental stages. Kawooya, J. K. 1983. Electrophoretic discrimination


of species of the Muscidifurax ( Hymenoptera raptor ( Hymenoptera Pteromalidae) influences

Pteromalidae) complex. Ph.D. Dissert, Univ. of their longevity and fecundity. Ann. EntomoL Soc.Illinois, Urbana. 113 pp. Am. 60: 678-691.

Kogan, M. and E. F. Legner. 1970. A biosystematic Legner, E. F., E. J. Dietrick, and D. J. Blehm. 1982.

revision of the genus Muscidifurax ( Hymenoptera: New parasitic insects for biological control of

Pteromalidae) with descriptions of four new synanthropic flies. Proc. Calif. Mosq. Vectorspecies. Canal Entomol. 102: 1268- 1290. Contr. Assoc. 50: 45-47.

Krell, P. J. and D. B. Stoltz. 1979. Unusual baculovirus Mane, S. D., L. Tompkins, and R. C. Richmond. 1983.

of the parasitoid wasp, Apanteles melanoscelus: Male esterase 6 catalyzes the synthesis of a sexisolation and preliminary characterization. J. pheromone in Drosophila melanogaster females.Virol. 29: 1118- 1130. Science ( Washington, D.C.) 222: 419-421.

Legner, E. F. 1967. Behavior changes the reproduction McCoy, C. W. 1967. Biosystematic and field studies ofof Spalangia cameroni, S. endius, Muscidfurax two parasites of the Muscidifurax raptor complex

raptor, and Nasonia vitripennis ( Hymenoptera Hymenoptera: Pteromalidae) with particular

Pteromalidae) at increasing fly host densities. Ann. reference to sex determination. Ph.D. Dissert.,Entomol. Soc. Am. 60: 819-826. Univ. of Calif., Riverside. 166 pp.

Legner, E. F. 1979. Prolonged culture and inbreeding Morgan, P. B. 1981. The potential use of parasites to

effects on reproductive rates of two pteromalid control Musca domestica L. and other filth

parasites of muscoid flies. Ann. Entomol. Soc. breeding flies at agricultural installations in theAm. 72: 114- 118. southern United States. Pp. 11- 25, in Status of

Biological Control of Filth Flies, U. S. Dept.Legner, E. F. 1985a. Natural and induced sex ratio Agric., A 106.2 ( F-64).

changes in populations of thelytokous

Muscidifurax uniraptor ( Hymenoptera Ptero- Mudd, A. R., C. Fisher, and M.C. Smith. 1982. Volatile

malidae). Ann. Entomol. Soc. Am. 78: 398-402. hydrocarbons in the Dufour' s gland of the parasiteNemeritis canescens ( Gray.) ( Hymenoptera:

Legner, E. F. 1985b. Effects of scheduled high Ichneumonidae). J. Chem. Ecol. 8: 1035- 1042.temperature on male production in thelytokous

Muscidifurax uniraptor ( Hymenoptera Ptero- Mullen, B. A.,J. A. Meyer, and J. D. Mandeville. 1986.malidae). Canal EntomoL 117: 383- 389. Seasonal and Biel activity of filth fly parasites

Hymenoptera: Pteromalidae) in caged- layerLegner, E. F. 1986. Breeding superior parasitoids of poultry manure in southern California. Environ.

Diptera using a novel extranuclear inheritance Entomol. 15: 56-60.

mechanism. Proc. Calif. Mosq. Vector Contr.Assoc. 54: 156- 159. Petersen, J. J. and J. A. Meyer. 1983. Host preference

and seasonal distribution of pteromalid parasitesLegner, E. F. 1987a Transfer of thelytoky to Hymenoptera: Pteromalidae) of stable flies and

anhenotokous Muscidifurax raptor Girault and house flies ( Diptera: Muscidae) associated withSanders ( Hymenoptera Pteromalidae). Canad. confined livestock in eastern Nebraska. Environ.

Entomol. 119: 265-271. EntomoL 12: 567-571.

Legner, E. F. 1987b. Inheritance of gregarious and Richmond, R. C. and A. Senior. 1981. Esterase 6( ECsolitary oviposition in Muscidifurax raptorellus 3. 1. 1. 1.) of Drosophila melanogaster: kinetics ofKogan and Legner ( Hymenoptera: Pteromolidae). transfer to females, decay in females and maleCanal Entomol. 119: 791- 808. recovery. J. Insect. Physiol. 27: 849- 854.

Legner, E. F. and D. Gerling. 1967. Host-feeding and ROssler, Y. and P. DeBach. 1972. The biosystematicoviposition on Musca domestica by Spalangia relations between a thelytokous and ancameroni, Nasonia vitripennis, and Muscidifurax arrhenotokous form of Aphytis mytilaspidis


Baculovirus-like particles in the reproductiveLeBaron) ( Hymenoptera: Aphelinidae). 1. The tracts of female parasitoid wasps. Canal. J.

reproductive relations. Entomophaga 17: 391-423. Microbiol. 22: 1013- 1023.

Rutz, D. A. and R. C. Axtell. 1979. Sustained releases Templeton, A. R. 1982. The prophecies ofof Muscidifurax raptor ( Hymenoptera: Ptero- parthenogenesis. Pp. 75- 101, in: Evolution andmalidae) for house fly (Musca domestica) control Genetics of Life Histories. ( H. Dingle and I. P.in two types of caged- layer poultry houses. Hagmann, eds.), Springer-Verlag, New York/Environ. Entomol. 8: 1105- 1110. Berlin.

Stanley-Samuelson, D. W. and W. Loher. 1986. Vinson, S. B. and D. B. Stoltz. 1986. Cross-protectionProstaglandins in insect reproduction. Ann. experiments with two parasitoid ( Hymenoptera:Entomol. Soc. Amer. 79: 841- 853. Ichneumonidae) viruses. Ann. Entomol. Soc. Am.

79: 216-218.Steel, R. G. D. and J. H. Tome. 1960. Principles and

Procedures of Statistics with Special Reference to Webster, R. P. and R. T. Canie. 1984. The effects ofthe Biological Sciences. McGraw-Hill Book Co., mating, exogenous juvenile hormone and aInc., New York. 481 pp. juvenile hormone analogue on pheromone titre,

calling and oviposition in the omnivorousStoltz, D. B. and S. B. Vinson. 1977. Baculovirus-like leafroller moth ( Platynota stultana). J. Insect

particles in the reproductive tracts of female Physiol. 30: 113- 118.parasitoid wasps II: The Genus Apanteles. Canad.J. Microbiol. 23: 28-37. Werren, J. H., S. W. Skinner, and A. W. Huger. 1986.

Male-killing bacteria in a parasitic wasp. ScienceStoltz, D. B., S. B. Vinson, and E. A. Mackinnon. 1976. 231: 990-992.


SOME QUANTITATIVE ASPECTS OF INHERITANCE IN BREEDING

SYNANTHROPIC FLY PARASITOIDS

E. F. Legnerl

ABSTRACT: The inheritance of solitary and recessive gregarious oviposition behavior in two strains ofMuscidifurax raptorellus Kogan and Legner appears quantitative, as successive backcrosses of hybrids to originalparental males result in additive intensities of trait expression. The magnitude of each increase is dependent on thenumber of backcrosses that were performed to create the hybrid, the particular" load" of backcrosses that a hybrid

possesses determining the degree to which the next mating will affect behavior. The curve for increasing expressionof behavior appears sigmoid. Females changed their behavior significantly immediately following mating. Thus,for biological control the liberation of parasitoid males possessing certain desirable traits, such as high fecundityor parasitization rates might be a rapid way to enhance control of target hosts by causing expression of the trait inferal females with whom the males mate, as well as by the resultant offspring.

INTRODUCTION genus, Muscidifurax raptorellus Kogan and Legner,

occurs in distinctive populations. One strain from

The genus Muscidifurax ( Hymenoptera: coastal Peru is predominantly solitary, while anotherPteromalidae) contains a group of closely related from central Chile is > 60 percent gregarious in

parasitoid species which attack puparia of synanthropic ovipositional and developmental behavior at defined

Diptera and, thus, are beneficial in natural control. The host densities ( Kogan and Legner 1970, Legner 1967,

five described species occur in geographic isolation in 1987). The Chilean strain compensates a lower host

the Nearctic and Neotropics, except two species which searching capacity with gregarious behavior that nets aare sympatric in the western Nearctic ( Kawooya 1983, greater number of progeny per host( Legner 1967). In

Kogan and Legner 1970, Legner 1969, 1983). The this species the inheritance of certain behavioral traits is

suspected ancestor of this apparent clade, Muscichfurax known to involve a process whereby the femaleraptor Girault and Sanders, is distributed in Europe, parasitoid first expresses some of the trait shortly afterAfrica, North America, and portions of the Pacific area mating with the male bearing it, and then passes it to herLegner 1972, Legner and Olton 1968, 1971, Legner et offspring where it is fixed into their genome and

al. 1976); but has not been found in the Neotropics and demonstrated in the virgin state ( Legner 1986).

there are no known clinal patterns. The genus has not Extranuclear phenomena were thought to be involved

been reported from Asia and is poorly represented in in this scheme which was called" accretive inheritance."

humid equatorial regions ( Legner 1983, Legner and The present study was performed to measure theGreathead 1969, Legner and Olton 1968, Legner et al. fixation of heritable behavior in a succeeding series of1976). backcrosses to hybrids created through reciprocal

Muscidifurax spp. are most prevalent in or near crosses between the Peruvian and Chilean strains of M.

accumulated decaying organic wastes deposited by raptorellus for the purpose of breeding superiorhumans or their livestock where they parasitize host parasitoids for biological control.

Diptera that also breed selectively in this habitat. Thus,they fit the endophilous eusynanthropic category MATERIALS AND METHODS

Legner et al. 1974, Povolny 1971), and their existencelargely is dependent on herdsmen. This has led to the To study fecundity and parasitization, cohorts of 10suggestion that the four species presently confined one-day-old female parasitoids were isolated inwholly to the Americas could have evolved within the screened, 46 cm' polystyrene vials with a basal area of

recent time period of European settlement or during the 7 cm 2. Females were either allowed to remain virgins

past 400 years( Kogan and Legner 1970, van den Assem or were mated to Chilean or Peruvian males for one day.and Povel 1973). Fart female was supplied daily with 20 24-to 30-h-old

The only known South American member of the puparia of Musca domestica L., 6.4± 0.5 mm X 2.8± 0.2

University of California, Division of Biological Control, Riverside, CA 92521, USA.


mm, distributed randomly over the vial base, and which second through tenth days of oviposition, their dailyhad been reared until pupation using commercial values approximating the averages shown in TABLESCSMA® medium. Parasitization efficiency at this host 1 and 2 ( note low standard deviations).density and in this environment at 25.5° C was nearoptimum ( Legner 1967, 1979). Effects of Mating on Female Behavior

Host puparia that were exposed to parasitoids for Females changed their behavior significantly24-h were incubated at 25.5± 1° C, 55 percent RH, and following mating, as previously observed in this speciesa 13L: 11D photoperiod supplied by fluorescent lamps, ( Legner 1986). A Chilean male of gregarious heritagegiving a table- level intensity of ca. 25 ft-c( 269 lux) until mated to a Peruvian female caused her to lay signifi-adult flies ceased to emerge and died( ca. 9 days). The cantly more eggs gregariously. However, Peruvianremaining puparia were then incubated separately in males of solitary heritage significantly reduced thegelatin capsules ( 10 X 25 mm) for the emergence of F1 gregarious capability of Chilean females with whomparasitoid progeny. Unemerged puparia were dissected they mated ( TABLES 1, 3, and 5). This was truefor aborted parasitism. whether the matings were with females of each original

Parasitoid longevity, total progeny, and sex ratio strain or their hybrids( FABLES 1 and 2). Also, Chileanwere recorded for each female for 16 days, which is ca. females mated to males of their own species tended tothe one-half life expectancy of a population of females. increase gregarious oviposition and significantlyThe importance of extended experimental time for increased the number of hosts they parasitized if theviewing behavior accurately is becoming recognized mating was with a Peruvian male ( TABLE 1) whosefor other parasitoids ( Hey and Gargiulo 1985) and strain had a distinctively higher oviposition rateDrosophila ( Templeton 1982). TABLE 2). However, no other significant quantitative

Three series of identical experiments with slight effects were noted with host attack rates and matingtemperature and replicate modifications were ( TABLE 3). Dissections of unemerged puparia andconducted over a two year period, but the results aliquot replicates in these experiments eliminated thereported herein consider only the last experiment, possibility of differential egg or larval mortality, andwhich did not differ appreciably from the previous two. verified variable intensities of solitary or multiple ovi-

Experiments were conducted in a completely positions as true behavioral changes following matings.random design. Analyses of variance were performed Mother comparatively weaker measurementon the binomial data transformed as follows: the arcsin pertaining to oviposition behavior was the total numberof the square-root of the percent response was used for of parasitoids that developed per gregariouspercent gregarious oviposition; the square-root of X+ 1/ oviposition. These showed many significant parallel2 for number of parasitoids per gregarious oviposition; trends with percent gregarious oviposition ( TABLES 1and the log( base 10) of X+ 1/ 2 was used for total hosts and 2). Ancestral Chilean virgins produced the highestparasitized ( Steel and Torrie 1960). Duncan' s ( 1955) average number of parasitoids ( 3. 13 to 3.33) permultiple range tests were performed on the transformed gregarious oviposition, but all subsequent hybridsdata, and although only the P<0.05 level is shown, possessing various proportions of Peruvian heritagesignificance was frequently detected at P<0.01 or less. never attained this high level ( TABLES 1 and 2).

Gregarious behavior was entirely eliminated in the thirdRESULTS backcross to Peruvian males ( TABLE 2).

Reciprocal crosses of the two M. raptorellus strains Quantitation of Inheritanceproduced offspring which were heterozygous for TABLES 1 and 2 also show details of the pathwayssolitary and gregarious oviposition, ( TABLES 1 and 2). to inheritance of gregarious and solitary ovipositionResultant Fl hybrids appeared heterotic with respect to behavior. The average daily percent gregariousgreater parasitization rates ( TABLE 3). ovipositions for the Chilean strain of M. raptorellus

Successive backcrosses to either original parental ranged from 80.9 to 66.6 percent for mated and virginmale produced hybrids which showed either females, respectively; while no gregarious ovipositionquantitative increases or decreases in the percent of was observed in the Peruvian strain( TABLE 1). Matinghosts that were parasitized gregariously and in the Peruvian males with Chilean females reduced thenumber of parasitoids developed per host ( TABLES 1 latter' s gregarious virgin oviposition significantly toand 2). The expressions of gregarious behavior were 56. 1 percent, a quantitative drop of 15.8 percent.remarkably uniform among replicate females from the However, mating Chilean males with Peruvian females


caused the latter to increase their virgin gregarious 0.923, 33 df), and total progeny ( r - 0.858, 34 df) as

oviposition rate significantly to 8.5 percent( TABLE 1). calculated over all tests. Sex ratios among offspring ofThe virgin hybrids of these crosses possessing mated parents ranged from 62 to 80 percent females,

inheritance from both Chilean and Peruvian parents with no significant trends being related to inheritance.showed gregarious oviposition capabilities that were The magnitude of behavioral expression that was

ca. two-thirds reduced from Chilean virgins ( TABLES evoked in females by mating with either a Peruvian or1 and 2). However, as in the case of their parents, a Chilean male was ca. one-half that observed

matings with Chilean males increased their gregarious subsequently in resultant hybrid progeny. This can beperformance, while Peruvian males reduced it( FABLE seen by referring to the values for virgin hybrids in1). These differences were all significant at < 0.05 TABLES 1 and 2. The origin of males from haploid ova

percent, as tested by Duncan' s ( 1955) multiple range in these Hymenoptera might logically explain thistest. Similar results are found in the first, second, and quantitative difference, while in diploid virgin hybrids

third backcrosses ( TABLES 1 and 2). the particular expression ca. doubles.

There were significant (< 0.01) positive correla- The quantity of gregariousness or solitariness thattons between the percent of gregarious ovipositions was inherited in each backcross differed according toand the number of individuals oviposied per host ( r= the " load" that each hybrid possessed for either trait.

TABLE 1. Quantitative inheritance of gregarious oviposition behavior by the Peruvian strain of Muscid-ifurax raptorellus Kogan and Leper: 10 females ovipositing continuously at 25° ± 1° C., 55%

RH on 20 Musca domestica L. puparia daily for 16 days.

AVERAGE NO. PER DAY/ Stand.-dev.

Gregarious Oviposition' Parasitoids developed per host'

Female Female Female Female

Virgin Mated to Mated to Virgin Mated to Mated to

Lineage of Female Female Chile Male Peru Male Female Chile Male Peru Male

P, Peru Female 0 8. 5 0 1. 00 2.00 1. 00

4. 9) 0) 0.22) ( 0)

F, hybrids with Chile Male 19.48

48.5b

10.4` 2.07' 2. 35b 2.038

4. 5) ( 9. 3) 4.5) 0. 19) ( 0. 10) 0.31)

Backcrosses to Chile Male

1st 64. 58 68.28 43.0b 2.658 2.94b 2.57'

14. 6) ( 9.2) 11. 0) 0.40) ( 0.33) 0.47)

2nd 66.3a75.

9b 34.8' 2.84' 3. 26' 2. 18b

9. 1) ( 5.2) 3. 1) 0.42) ( 0. 14) 0.04)

3rd 78.2 2.92

5.2) 0.40)

Backcrosses to Peru Male

1st 1. 3' 28. 8b 2. 3a 2.00' 2. 15' 2.22'

1. 3) ( 10. 8) 1. 8) ( 0) 0. 11) 0.70)

2nd 1. 5 2.001. 8) 0)

Values within a row followed by the same letter are not significantly different ( P<0.05; Duncan' s [ 1955]multiple range test).


For example, hybrids with a single gregarious ancestor Peruvian male decreased the expression by 93.3were capable of expressing a higher rate of gregarious percent. However, in the second backcross the additionbehavior if mated with a Chilean male than those whose of either Chilean or Peruvian influences through matinglineage showed one, two, or three backcrosses to a caused increases or decreases whose magnitudeChilean male ( TABLES 1 and 2). Similarly, hybrids depended on the lineage of the hybrid( TABLES 1 andbackcrossed to a Peruvian male progressively lost 2). The curve for adding additional magnitudes ofgregarious instincts, with the rate of loss decreasing gregarious or solitary ovipositional expression,only slightly after the first backcross. The reflections of beginning with the original parental strain, and throughthese gains or losses were obvious in the resultant the first, second, and third backcrosses, seems sigmoidprogeny of the mated hybrids( TABLES 1 and 2). Thus, ( refer to data for virgin females in TABLES 1 and 2).backcrossing a 19.4 percent gregarious F, hybrid to a Because males are able to activate portions of theirChilean male increased gregarious expression in virgin genetic make-up within their own generation, throughprogeny by 232 percent, whereas, the backcross to a causing immediate expression of some unique traits in

TABLE 2. Quantitative inheritance of gregarious oviposition behavior by the Chilean strain of Muscidi-furax raptorellus Kogan and Legner: 10 females ovipositing continuously at 25°± 1° C., 55%

RH on 20 Musca domestica L. puparia daily for 16 days.

AVERAGE NO. PER DAY / Stand.-dev.

Gregarious Oviposition' Parasitoids developed per host'Female Female Female Female

Virgin Mated to Mated to Virgin Mated to Mated toLineage of Female Female Peru Male Chile Male Female Peru Male Chile Male

P, Chile Female 66. 6° 56. 1" 80.9' 3. 13' 2. 56" 3. 33'14. 5) ( 7.7) 9. 5) 0.67) 0.22) 0.52)

F, hybrids with Peru Male 21. 1' 8. 1" 41. 4° 2. 10' 2. 10' 2.3?5. 3) ( 2. 1) 6.8) 0.07) ( 0. 18) 0. 12)

Backcrosses to Peru Male1st 5. 1° 3. 5° 22.5" 2.00' 2.00° 2. 10°

3. 9) ( 0. 1) 6. 8) 0) 0) 0. 10)

2nd 0.4' 0.2° 2.00° 2.00° 0.8) ( 0.2) 0) 0)

3rd 0 0 1. 00° 1. 00'

0) 0)

Backcrosses to Chile Male1st 61. 8° 29. 1" 66.3' 2.536 2. 23' 2.78"

12.0) ( 11. 0) ( 13.6) 0.35) 0. 16) 0. 22)

2nd 69. 7° 35. 1" 68. 3° 2.72° 2. 29" 2.8?6.6) ( 15. 1) 3. 1) 0.23) 0.23) 0.28)

3rd 81. 9 - 3. 12

0.67)



TABLE 3. Total hosts parasitized by the Peruvian and Chilean strains of Muscidifurax raptorellus Koganand Legner and their hybrids: 10 females ovipositing continuously at 25°± 1° C. and 55% RH

on 20 Musca domestica L. puparia for 16 days.

AVERAGE TOTAL HOSTS PARASI L IZED / Stand.-dev.

Original Peru Female Line Original Chile Female Line'

Female Female Female Female

Virgin Mated to Mated to Virgin Mated to Mated to

Generation Female Peru Male Chile Male Female Peru Male Chile Male

F, 84.2 85.0 79.5 43.0' 71. 8b 53. 0'

16.7) ( 11. 4) 18.9) 18. 7) 18.7) 25.3)

F, Hybrids 102.7 106.2 95.2 109.0 113. 1 105.0

10. 1) ( 16.4) 23.7) 12. 1) 12.0) 23.6)

Backcrosses to Chile Male

1st 94.0 81. 6 95.7 84.0 88.8 114. 8

14. 2) ( 25.8) 19. 8) 22.2) 24. 1) 10.5)

2nd 98.6 78.7 90. 1 97.4 93.2 113. 8

13. 9) ( 13. 1) 15. 5) 7. 1) 14. 1) 12. 1)

3rd 113. 8 112.5

13. 1) 9.9)

Backcrosses to Peru Male

1st 70.4 84.4 80.8 74.8 78.4 89.4

17. 2) ( 17.7) 16.4) 15. 1) 15. 8) 15. 3)

2nd 99.8 55.2 65.2

9.6) 14.5) 16. 1)

3rd 80.2 82.2

14.2) 16.4)


the females with whom they mate, selection pressure Acknowledgments

begins within their own generation, not having to waitfor expression in the F, progeny. Thus, not only may I am especially grateful to Dr. J. C. Luhman for hisfunctional haploid parasitoid males provide a means for assistance and diligence in counting data of preliminarythe rapid elimination of unfavorable genes, as suggested experiments which established behavioral trends and to

by Dobzhansky ( 1941), but they may serve to quicken Mr. R. W. Warkentin for his care in the preparation of

the pace of natural selection for both nonlethal age-classed hosts and parasitoids. Financial support

undesirable and desirable characteristics as well. For was provided by Rincon-Vitova Insectaries, Inc.inundative biological control, the liberation of males

possessing certain desirable traits, such as high fecun- REFERENCES CITED

dity or parasitization rates might cause feral residentfemales with whom they mate to enhance their impact Dobzhansky, T. 1941. Genetics and the Origin of

against the target host, as well as produce a hybrid Species. 2nd Ed. Columbia Univ. Press, New

population that demonstrates such qualities. York, 428 pp.


Assoc. 54: 156- 159.Duncan, D. B. 1955. Multiple range and multiple F

tests. Biometrics 11: 1- 41. Legner, E. F. and D. J. Greathead. 1969. Parasitism ofpupae in East African populations of Musca

Hey, J. and M. K. Gargiulo. 1985. Sex- ratio changes in domestica and Stomoxys calcitrans. Ann.Leptopilina heterotoma in response to breeding. J. Entomol. Soc. Am. 62: 128- 133.of Heredity 76: 209-211.

Legner, E. F. and G. S. Olton. 1968. Activity ofKawooya, J. K. 1983. Electrophoretic discrimination parasites from Diptera: Musca domestica,

of species of the Muscidifurax ( Hymenoptera: Stomoxys calcitrans, and species of Fannia,Pteromalidae) complex. PhD. Dissert., Univ. of Muscina, and Ophyra II. At sites in the EasternIllinois, Urbana, 113 pp. Hemisphere and Pacific area. Ann. Entomol. Soc.

Am. 61: 1306- 1314.Kogan, M. and E. F. Legner. 1970. A biosystematic

revision of the genus Muscidifurax ( Hymenoptera: Legner, E. F. and G. S. Olton. 1971. Distribution andPteromalidae) with descriptions of four new relative abundance of dipterous pupae and theirspecies. Canad. Entomol. 102: 1268-2190. parasitoids in accumulations of domestic animal

manure in the southwestern United States.Legner, E. F. 1967. Behavior changes the reproduction Hilgardia 40: 505-535.

of Spalangia cameroni, S. endius, Muscidifuraxraptor, and Nasonia vitripennis ( Hymenoptera: Legner, E. F., I. Moore, and G. S. Olton. 1976. TabularPteromalidae) at increasing fly host densities. Ann. keys and biological notes to the commonEntomol. Soc. Am. 60: 819-826. parasitoids of synanthuopic Diptera breeding in

accumu- laced animal wastes. Entomol. News 87:Legner, E. F. 1969. Reproductive isolation and size 113- 144.

variation in the Muscidifurax raptor complex.Ann. Entomol. Soc. Am. 62: 382-385. Legner, E. F., R. D. Sjogren, and I. M. Hall. 1974.

Biological control of medically important arthro-Legner, E. F. 1972. Observations on hybridization and pods. Crit. Rev. Environ. Contr. 4: 85- 113.

heterosis in parasitoids of synanthropic flies. Ann.Entomol. Soc. Am. 65: 254-263. Povolny, D. 1971. Synanthropy: definition, evolution,

and classification. Pp. 17- 54, in Flies and Diseace,Legner, E. F. 1979. Prolonged culture and inbreeding Ecology, Classification and Biotic Associations (

effects on reproductive rates of two pteromalid B. Greenberg, ed), Vol. I. Princeton Univ. Press,parasites of muscoid flies. Ann. Entomol. Soc. Princeton, NJ, 856 pp.Am. 72: 114- 118.

Steel, R. G. D. and J. H. Torrie. 1960. Principles andLegner, E. F. 1983. Broadened view of Muscidifurax Procedures of Statistics with Special Reference to

parasites associated with endophilous the Biological Sciences. McGraw-Hill Book Co.,synanthropic flies and sibling species in the Inc., NY, 481 pp.Spalangia endius complex. Proc. Calif. Mosq.Vector Contr. Assoc. 51: 47-48. Templeton, A. R. 1982. The prophecies of

parthenogenesis. Pp. 75- 101, in Evolution andLegner, E. F. 1985. Natural and induced sex ratio Genetics of Life Histories ( H. Dingle and I. P.

changes in populations of thelytokous Hagmann, eds.), Springer-Verlag, New York/Muscidifurax uniraptor ( Hymenoptera: Berlin.Pteromalidae). Ann. Entomol. Soc. Am. 78:

398- 402. van den Assem, J. and G. D. Povel. 1973. Courtshipbehavior of some Muscidifurax species ( Hym.,

Legner, E. F. 1986. Breeding superior parasitoids of Pteromalidae): a possible example of a recentlyDiptera using a novel extranuclear inheritance evolved ethological isolating mechanism.mechanism. Proc. Calif. Mosq. Vector Contr. Netherlands J. Zool. 23: 465-487.


MEDICALLY IMPORTANT AND OTHER ECI'OPARASITIC ACARINES ON

VERTEBRATES FROM SANTA CATALINA ISLAND, CALIFORNIA

S. G. Bennett'

Santa Catalina Island is one of eight Channel most frequently on their hosts in the winter. Eggs thatIslands which lie off the coast of southern California( 32 hatch in the spring produce larvae which diapause untilkm from Los Angeles) and is the least studied of the the fall ( Furman and Loomis, 1984). The two adult

Channel Islands as relates to mites and ticks. Lane et al. females collected by the author were found alive1983) reported argasid and ixodid ticks from the other beneath rocks near deer trails.

Channel Islands, but only mentioned the record ofIxodes pacificus from Santa Catalina taken by Gus Ixodes brunneus

Augustson in January of 1941( Cooley and Kohls, 1945) A common parasite of birds found throughout the

during the Channel Islands Biological Survey of 1939- United States. The only records presented here are from1941. Cooley and Kohls ( 1945) also recorded Ixodes Cooley and Kohls ( 1945).brunneus from Santa Catalina Island and Furman and

Loomis ( 1984) listed I. pacificus, I. brunneus, and Ixodes pacific us ( Western Black- legged Tick)

Dermacentor albipictus. This is the most common species of Ixodes in

Although the insular endemic tick Ixodes California, particularly in coastal regions, and is theperomysci occurs on some of the other California most important with regards to human health. Nymphs

Channel Islands, it has not yet been reported from Santa and adults will readily bite man and domestic animalsCatalina Island. The larval trombiculid mites( chiggers) such as dogs and horses. One adult female was found

Eutrombicula belkini and Kayella lacerta were attached to the author's stomach after walking through

reported from East Anacapa Island by Powder and high grass and coastal sage. Epidemiological evidence

Loomis( 1962), but no published records exist for these suggests that I.pacificus is responsible for transmittingrelatively common lizard ectoparasites from Santa the Lyme Disease spirochaete( Borrelia burgdorferi) to

Catalina Island. All other records of acarines presented humans in California. Ixodes pacificus is a winter tick

in this paper are new for Santa Catalina Island and and is most active from November through Mayspecimens collected from 1979 to 1987 were taken by ( Furman and Loomis, 1984). The collection of larvae

the author unless otherwise noted. This represents a and nymphs from the side-blotched lizard ( Uta

preliminary study of ectoparasitic acarines from Santa stansburiana), the skink ( Eumeces skiltonianus),

Catalina. Host, date, and locality data for all records are and one adult from a goat ( Capra hirca) on Santa

presented in TABLES 1 and 2. Additional references Catalina Island all constitute new records for this

used for specimen identification included Evans and tick.

Till ( 1966), Krantz ( 1978), and McDaniel ( 1979) for

mesostigmata; Bennett ( 1977), Brennan and Goff MACRONYSSIDAE

1977), and Loomis ( 1956, 1971) for tmmbiculidae. Ornithonyssus bacoti ( Tropical Rat Mite)

A single specimen was recovered from a small

DISCUSSION child in the city of Avalon. All members of the child' sfamily had suffered from numerous red pustules on their

IXODIDAE bodies and severe itching for several weeks followingDermacentor albipictus ( Winter Tick) the removal of a rat infested tree adjacent to their home.

This tick occurs primarily on large herbivorus The mite was seen crawling on the child' s body and wasmammals ( most commonly on horses and deer) and is removed with a piece of tape by the mother. The

widely distributed throughout North America, specimen was mounted on a slide and cleared in

including coastal California. Activity of larvae begins Polyvinyl Alcohol-Lactic Acid mounting media.in September with larvae and nymphs being found on Additional mites were recovered from a single Rattus

their hosts from September through April. Adults are rattus at Toyon Bay.

Orange County Vector Control District, 13001 Garden Grove Blvd., Garden Grove, CA 92643 USA.


Ornithonyssus sylviarum ( Northern Fowl Ophionyssus natricis ( Snake Mite)Mite) Common parasite of snakes and lizards,

Hundreds of larvae, nymphs, and adults were particularly in zoos and pet shops and is the vector of theremoved from an abandoned Barn Swallow ( Hirunda bacterium Pseudomonas hydrophilus which causesrustica) nest where they were exiting the nest and hemorrhagic septicemia in captive reptiles. It has alsocrawling down the wall of a building and onto the been recorded from rats and humans( McDaniel 1979).floor. Gravid females were recovered from two alligator

TABLE 1. Records of ectoparasitic acarines from Santa Catalina Island.

L NM F Locality Date Host or Source

METASTIGMATAIxodidae

Dermacentor 1 3 5 None IX- 14- 48 Odocoileus hemionus ( Mule Deer)albipictus 7 12 None IX-2-49

x x None II-2- 491 Toyon Bay III-6-80 Under rock1 Blackjack Mtn. XII- 1- 84

xodes brunneus Los Angeles Co. II-29-40 Lanius ludovicianus ( Loggerhead Shrike)

lxodes pacificus 1 Santa Catalina Isl. I- 23- 41 Lophortyx californicus ( California Quail)1 6 2 None IX- 14- 48 Odocoileus hemionus

2 None XI-2- 491 Isthmus Cove IV-6-79 Gerrhonotus multicarinatus( Alligator Lizard)1 Isthmus Cove IV-8- 79 Uta stansburiana ( Side-blotched Lizard)

2 3 Isthmus Cove X1- 13- 87 On Clothing1 Isthmus Cove X1- 14-87 Human

3 5 Toyon Canyon V-2- 80 Gerrhonotus multicarinatus1 8 Toyon Canyon II-22-81

1 Toyon Canyon I- 30- 82 Uta stansburiana1 Toyon Canyon II-21- 82 Uta stansburiana

1 Toyon Canyon XII-12- 85 Urocyon littoralis ( Island Fox)1 Toyon Canyon III-22-86 Canis familiaris ( Domestic Dog)

1 Toyon Canyon I- 11- 86 Capra hirca ( Goat)2 Toyon Canyon II-14- 87 Sus scrofa ( Wild Pig)2 Toyon Canyon I- 17- 87 Tick drag

4 Toyon Bay III-2- 81 Gerrhonotus multicarinatus1 2 Toyon Bay XII-4-82 Urocyon littoralis2 Bullrush Canyon II-21- 81 Gerrhonotus multicarinatus1 Gallaghers Cyn. V- 14- 81 Eumeces skiltonianus ( Western Skink)

5 Gallaghers Cyn. II-5- 82 Canisfamiliaris1 Blackjack Mtn. I- 26- 85 On clothing1 Blackjack Mtn. XII-1- 85 On clothing

MESOSTIGMATAMacronyssidae

Ornithonyssus bacoti 1 Avalon V-4- 84 Human5 Toyon Bay VI-27- 87 Rattus rattus ( Roof rat)

Ornithonyssus sylviarum x x x x Toyon Bay VI-29- 81 Barn Swallow nest( Hirundo rustica)Pellonyssus passeri x x x x Toyon Bay V-20- 82 Selasphorus Basin ( Allen's Hummingbird)Ophionyssus natricis 10 Isthmus Cove XI- 14- 87 Gerrhonotus multicarinatus

Dermanyssidae

Dermanyssus gallinae x x x x Toyon Bay VII-5- 86 Barn Swallow nest

L= larvae; N= nymphs; M= adult male; F= adult female; x= unknown#.


TABLE 2. Records of ectoparasitic acarines from Santa Catalina Island.

L NM F Locality Date Host or Source

PROSTIGMATA

Trombiculidae

Eutrombicula belkini 4 Isthmus, V- 11- 79 Uta stansburiana

Catalina Harbor

10 VI- 1- 79 Uta stansburiana

3 Cherry Cove IV-8-79 Uta stansburiana

9 Cape Canyon V-25- 80 Uta stansburiana

10 Toyon Canyon V- 17- 80 Uta stansburiana

5 Toyon Canyon X-23- 81 Uta stansburiana

1 Toyon Canyon VI-28- 87 Spermophilus beecheyi( Ground squirrel)

5 Gallahers Cyn. V- 14- 81 Eumeces skiltonianus

Euschoengastia ambocalis 2 Toyon Bay V 81 Peromyscus maniculatus( Deer Mouse)

1 Bullrush Cyn. XII-2-84 Soil sample

12 Isthmus Cove XI-14- 87 Reithrodontomys megalotis( Harvest Mouse)

Euschoengastia numerosa 1 Blackjack Cyn. XII-1- 84 Soil sample

Euschoengastoides ( nr.) 1 Haypress Reserv. VI-27- 87 Spermophilus beecheyi

neotomae

Kayella lacerta 3 Haypress Reserv. VI-27- 87 Spermophilus beecheyi2 Gallaghers Cyn. V- 14- 81 Eumeces skiltonianus

Acomatacarus arizonensis 2 Cape Canyon V-25- 80 Uta stansburiana

5 Toyon Canyon XI-7- 81 Uta stansburiana

Myobiidae

Pteracarus( nr.)chalinolobus 1 Toyon Bay IX-29- 81 Myotis evotis ( Long-eared Bat)

L= larvae; N= nymphs; M= adult male; F= adult female; x= unknown#.

lizards ( Gerrhonotus multicarinatus). associated with the side-blotched lizard ( Uta

Pellonyssus passeri stansburiana) on Santa Catalina Island. It attaches

Several specimens were removed from an injured primarily under the folds of skin on the neck. MammalsAllen' s Hummingbird ( Selasphorus sasin). The genus often serve as host for this mite which can cause severe

was described by Clark and Yunker ( 1956) from itching and dermatitis in humans ( Webb et al. 1983;specimens removed from English Sparrows ( Passer Bennett and Webb 1985). Unfed larvae may occur indomesticus). large numbers along coastal sagebrush- grassland

transitions during hot, humid summer months. LarvaeDERMANYSSIDAE climb up the vegetation and attach to passing hosts uponDermanyssus gallinae which they feed on tissue fluids for several days. When

Larvae, nymphs, and adults were recovered from engorged, the larvae drop from the host to the soil whereabandoned nest material of a barn swallow ( Hirunda they develop into free- living nymphs. The adult stagesrustica). are also free-living and, like the nymphs, prey on soil

arthropods and their eggs.

TROMBICULIDAE

Eutrombicula belkini ( California Pest Euschoengastia ambocalis and Euschoengas-

Chigger) tia numerosa

This is one of the most common trombiculid mites Unfed larvae of these chigger mites were recovered


from soil taken from groves of Lyonothamnus of Myotis evotis ( preserved in alcohol) from Toyonfloribundas floribundus, the Catalina Ironwood Tree, Bay.after samples were put in modified Tullgren Funnels forextraction of arthropods. Additional specimens of E. Acknowledgmentsambocalis were obtained from the ears of threePeromyscus maniculatus that had been preserved in I am grateful to Professor Deane P. Furman,alcohol since 1981 and two Reithrodontomys megalotis University of California, Berkeley, for providingtrapped near a rock outcropping. Euschoengastia additional records of ticks from Santa Catalinaambocalis was described by Wrenn and Loomis( 1973) Island; Dr. Robert S. Lane, University of California,from San Diego, California. It is found throughout Berkeley, for identifying tick specimens; Dr. Williamsouthern California on rodents, including P. J. Wrenn, University of North Dakota, for helpmaniculatus and R. megalotis, both of which occur on identifying trombiculid mites; Dr. James P. Webb,Santa Catalina Island. Euschoengastia numerosa was Orange County Vector Control District, Gardendescribed by Wrenn and Loomis ( 1974) from Ventura Grove, California, for assistance with the trombiculid,County, California from a scrub Jay ( Aphelocoma macronyssid, and myobiid mite identifications; Rosscoerulescens). This species has a broad host spectrum and Kristi Turner, Catalina Island Marine Institute,that includes several species of birds and mammals, Toyon Bay, Mr. Doug Propst and Terry Martin,including humans, and is widespread from southern Santa Catalina Island Conservancy, for providingCalifornia north to Oregon and Montana, east to Texas transportation and lodging while on the island;and south through Mexico. Karen Haberman, Catalina Island Marine Institute,

for her assistance in the field; and Mr. Gilbert L.Kayella lacerta Challet, Manager, Orange County Vector Control

Originally described by Brennan ( 1948) as District, for the use of laboratory facilities.Euschoengastia lacerta and later transferred to the

genus Kayella by Vcrcammen-Grandjean ( 1960). As REFERENCES CrIEDthe species name implies, the type series was ob-tained from a lizard, but since then it has been found Bennett, S. G. 1977. Trombiculid Mites on Lizardson a variety of mammals, including the ground squirrel From Southeastern Arizona M.A. thesis, Dept. ofSpermophilus beecheyi) on Santa Catalina Island. Biology, Calif. State Univ., Long Beach,

California, 192 pp.Acomatacarus arizonensis

This trombiculid species is found almost Bennett, S. G. and J. P. Webb. 1985. A possible humanexclusively on iguanid lizards in and portions of the infestation by Eutrombicula belkini ( Gould)southwestern United States and Mexico. Specimens Acari: Trombiculidae) in Laguna Beach,from Santa Catalina were removed from the iguanid, California Bull. Soc. Vector Ecol. 10(2): 118- 121.Uta stansburiana.

Brennan, J. M.and M.L.Goff. 1977. Keys to the generaEuschoengastoides ( nr.) neotomae of chiggers of the western hemisphere ( Acarina:

A single specimen of this chigger was removed Trombiculidae). J. Parasitol. 63(3): 554-566.from a ground squirrel ( Spermophilus beecheyi. It

appears to be closely related to Euschoengastoides Clark, G. M. and C. E. Yunker. 1956. A new genus andneotomae and Euschoengastoides hoplai. Additional species of Dermanyssidae ( Acarina: Mesostig-specimens will be required in order to properly identify mata) from the English Sparrow, with observationsthis species. on its life cycle. Proc. Helminth. Soc. Wash. 23(2):

92- 101.MYOBIIDAE

Pteracarus ( nr.) chalinolobus Cooley, A. and G. M. Kohls. 1945. The genus IxodesThese mites are parasitic on bats of the family in North America. U.S. Pub. Hlth Serv., Nat. Inst.

Vespertilionidae and have been found throughout the Hith. Bull. 184: 1- 246.world, including California and Nevada. The genus

was described by Jameson and Chow ( 1952) and Dusbabek, F. 1969. Generic revision of the myobiidwas discussed further by Dusbabek ( 1969 and 1973). mites( Acarina Myobiidae) parasitic on bats. FoliaA single male mite was removed from a specimen Parasitol. ( Praha) 16: 1- 17.


Dusbabek, F. 1973. A systematic review of the genus McDaniel, B. 1979. How to Know the Mites and Ticks.

Pteracarus ( Acariformes: Myobiidae). Acaro- Wm. C. Brown Co., Publ., Dubuque, Iowa, 335

logia, Tome XV, fasc. 2: 240-288. pp.

Evans, G. O. and W. M. Till. 1966. Studies on the Powder, W. A. and R. B. Loomis. 1962. A new species

British Dermanyssidae ( Acari: Mesostigmata) Part and new records of chiggers ( Acarina:

II: Classification. Bull, Brit. Mus. Natur. Hist. Trombiculidae) from reptiles of southern

14( 5): 1- 370. California. J. Parasitol. 48(2): 204-208.

Furman, D. P. and E. C. Loomis. 1984. The Ticks of Vercammen- Grandjean, P. H. 1960. Essai de

California ( Acari: Ixodida). Bull. Calif. Insect classification des larves de Trombiculinae Ewing,Survey 25: 1- 240. 1944. Acarologia 2(4): 469-471 ( chart).

Jameson, E. W., Jr. and C. Y. Chow. 1952. Pteracarus, Webb, J. P., R. B. Loomis, M. B. Madon, S. G. Bennett,

a new genus of myobiid mites ( Acarina: and G. E. Green. 1983. The chigger species

Myobiidae) from bats ( Mammalia• Chiroptera. J. Eutrombicula belkini Gould ( Acari: Trombi-

Parasitol. 38(3): 1- 4. culidae) as a forensic tool in a homicide

investigation in Ventura County, California. Bull.Krantz, G. W. 1978. A Manual of Acarology, 2nd Ed. Soc. Vector Ecol. 8(2): 141- 146.

Oregon State Univ. Book Stores, Inc., Corvalis,

Oregon. 509 pp. Wrenn, W. J. 1987. Key to larval EuschoengastiaAcari: Trombiculidae) in North America. J. Med

Lane, R. S., S. E. Miller, and P. W. Collins. 1983. Ticks Ent. 24(2): 221- 228.

Acari: Argasidae and Ixodidae) from the

California Channel Islands. Pan Pac. Ent. 58(2): Wrenn, W. J. and R. B. Loomis. 1973. A new species

96- 104. of Euschoengastia ( Acarina: Trombiculidae)

from western North America, and the status of E.

Loomis, R. B. 1956. The chigger mites of Kansas calfornica ( Ewing). J. Med. Ent. 10( 1): 97- 100.

Acarina Trombiculidae). Univ. Kansas Sci. Bull.

37( 19): 1195- 1443. Wrenn, W. J. and R. B. Loomis. 1974. The

Euschoengastia radfordi species complex

Loomis, It B. 1971. The genus Euschoengastoides Acarina Trombiculidae) from western North

Acarina: Trombiculidae) from North America J. America with descriptions of five new species.Parasitol. 57(4): 689-707. Ann. Ent. Soc. Am. 67(2): 241- 256.


THE INFLUENCE OF HOST BEHAVIOR ON SANDFLY ( LUTZOMYIALONGIPALPIS) FEEDING SUCCESS ON LABORATORY MICE

R. E. Colemanl and J. D. Edmanl

Numerous studies have shown that host Five-day old L. longipalpis were cold-anesthetized anddefensive" behavior can prevent mosquitoes from groups of 10, 20, 30, 40, 50, or 60 female flies placed in

successfully feeding on birds ( Edman and Kale 1971) holding cages without water or fructose. Experimentsand small mammals ( Day and Edman 1984, Klowden commenced 48 hours later with the introduction ofand Lea 1979, Waage and Nondo 1982, Walker and either an unrestrained or a restrained BALB/c mouseEdman 1986). Research has so far been limited to the ( Mus musculus) into the holding cage. Experimentseffect of defensive behavior on mosquitoes. We report were conducted early in the afternoon under fluorescenthere on the defensive behavior of laboratory mice light. Restrained mice were anesthetized withtowards sandflies. Nembutal and laid ventral surface down in the center of

Lutzomyia longipalpis ( Lutz and Neiva) were the cage. Remaining L. longipalpis were aspirated fromreared using the technique of Modi and Tesh ( 1983). the cage after one hour and the number of blood-fed flies

TABLE 1. Comparison of feeding success of Lutzomyia longipalpis on restrainedand unrestrained laboratory mice ( exposed for one hour).

SandflyHost Group No. of Total Blood % of

Condition Size Tests Flies Fed Total

Restrained 0- 10 2 15 3 ( 20.00)

11- 20 10 177 91 ( 51. 41)

21- 30 3 74 42 ( 56.75)

31- 40 0

41- 50 1 42 25 ( 59.52)

51- 60 1 55 26 ( 47.27)

Total 17 363 187 ( 51. 51)

Unrestrained 0- 10 2 17 0 ( 0.00)

11- 20 10 175 2 ( 1. 14)

21- 30 3 75 1 ( 1. 33)

31- 40 2 75 0 ( 0.00)

41- 50 0

51- 60 0

Total 17 342 3 ( 0.87)

Department of Entomology, University of Massachusetts, Amherst, MA 01003 U.S.A.


recorded. Each experiment was replicated 17 times. REFERENCES Cr1ED

Sandflies successfully fed on anesthetized mice,but were unable to feed on unrestrained animals Edman, J. D. and H. W. Kale II. 1971. Host behavior.

TABLE 1). Day and Edman ( 1984) found that Its influence on the feeding success of mosquitoes.laboratory mice were highly defensive towards Aedes Ann. Entomol. Soc. Am. 64: 513- 516.

aegypti, Anopheles quadrimaculatus, Culex

nigripalpis, and Culex quinquefasciatus. Unrestrained Day, J. F. and J. D. Edman. 1984. Mosquito

mice prevented mosquitoes from successfully feeding engorgement on normally defensive hosts dependsin most instances. We have found that unrestrained on host activity patterns. J. Med. Entomol. 21: 732-mice were equally as defensive towards L. longipalpis, 740.

allowing only a small portion of all flies to feed. This isthe first demonstration that the blood feeding success of Klowden, M. J. and A. 0. Lea. 1979. Effect of

Diptera other than mosquitoes is affected by host defensive host behavior on the blood meal size and

defensive responses. feeding success of natural populations ofmosquitoes( Diptera: Culicidae). J. Med. Entomol.

Acknowledgements 15: 514- 517.

The authors thank Dr. R. B. Tesh for the use of Modi, G. B. and R. B. Tesh. 1983. A simple technique

facilities at the Yale Arbovinis Research Laboratory for mass rearing Lutzomyia longipalpis and

and for providing sandflies for the experiments. The Phlebotomus papatasi ( Diptera: Psychodidae) in

invaluable aid of Mr. G. B. Modi and Mr. Whei-kuo Wu the laboratory. J. Med. Entomol. 20: 568-569.was greatly appreciated. This work was supported in

part by NTH Biomedical Research Grants # RR07048- Waage, J. K. and J. Nondo. 1982. Host behavior and

21 and # RR07048-20 and by a Joseph P. Healy mosquito feeding success: an experimental study.Endowment Fund Grant. Trans. Roy. Soc. Trop. Med. Hyg. 76: 119- 122.

Walker, E. D. and J. D. Edman. 1986. Influence of

defensive behavior of eastern chipmunks and greysquirrels ( Rodentia: Sciuridae) on feeding successof Aedes triseriatus ( Diptera: Culicidae). J. Med.

Entomol. 23: 1- 10.

BULL SOC. VECTOR ECOL, 12(2): 541- 543 DECEMBER, 1987

MALARIA TRANSMISSION IN THREE STYES SURROUNDING

THE AREA OF BOBO-DIOULASSO ( BURKINA FASO):

THE SAVANNA, A RICE MELD, AND THE CITY'

V. Robert2.3, P. Gazing, and P. Camevale2

Malaria is an endemic parasitic disease in West increased. Anopheles gambiae s. l. reached itsAfrica. At the end of the rainy season in rural areas, 70 maximum in August ( 25 bites/man/night), while An.to 90 percent of the children have parasites in their blood funestus reached its maximum in October ( 30 bites/Gazin, et al. 1985). The most frequently observed man/ night). Therefore, each inhabitant was

parasite is Plasmodium falciparum, the remainder are theoretically bitten by 7,500 Anopheles spp. per year.Plasmodium malariae, and very rarely Plasmodium Seventy-three percent of An. gambiae s.l. and 77ovale. Significant litres of malaria antibodies, as percent of An. funestus were parous, indicating highassessed by immunofluorescence assay, are found in all daily survival rate. Thus, a proportion of 21 percent ofadults ( Gazin et al. 1984). the adults would reach the age for malaria transmission

Although malaria is endemic, there are large ( Coz et al. 1961).differences in the intensity and the rhythm of the Sporozoites were observed in the salivary glands oftransmission from one area to another, as we have these two species from May to December. Theobserved in Bobo-Dioulasso and its neighbourhood. sporozoite index was 3 percent after 3,000 dissections.

Three sites were studied: Thus, every inhabitant was theoretically bitten by 135a traditional village, located 60 km north of Bobo- infected Anopheles spp. per year.

Dioulasso near a ephemeral marsh land.a village located in the middle of recently The village in the rice field.

developed rice fields, 30 km north of Bobo-Dioulasso, The main malaria vector was An. gambiae s. l.,where rice is harvested twice a year( Robert et al. 1985). while An. funestus was less represented. The vectorial

the city of Bobo-Dioulasso, including a peri- density was higher than in the savanna area. Anophelesurban district without any water distribution and gambiae s. l. was present all year long with large sea-collection system, and a central district, built over 30 sonal variations according to agricultural activity. Dueyears ago and with a minimum water supply collection to the rice cultivation in the dry season, the densityRobert et al. 1986). reached more than 40 bites/man/night. During the rainy

The anthrophilic anopheline fauna was studied by season rice cultivation, the density reached 80 bites/the usual all night catches on human beings. Caught man/night. Anopheles funestus was present only fromAnopheles were identified and dissected for classical September to December with a maximum of 6 bites/examination of ovaries and of salivary glands. man/night In these conditions, every inhabitant was

theoretically bitten 14,000 times per year by AnophelesRESULTS spp.

It has to be underlined that the anthropophilic An.The traditional village in the savanna. gambiae s. l. population was mainly composed of

Anopheles gambiae sensu lato and Anopheles nulliparous females ( 55%) indicating dispersion wasfunestus were predominant, while Anopheles nili was high and/or daily survival rate was short. Only 1. 9also noticed but at a low level. percent of the adults could reach the age suitable for

In January and February, during the cold, dry malaria transmission. The An.funestus population wasseason, Anopheles spp. were seen ( Fig. 1). From older with a parous rate of 73 percent. Such a highMarch, An. gambiae s. l. began to emerge( 5 bites/man/ nulliparous rate of An. gambiae s. 1. was one of thenight). When the rains began, the anopheline density explanations for the surprisingly low sporozoite index

Presented at the 1st European Branch Meeting, SOVE, Montpellier, FRANCE, 11- 12 September, 1986.2ORSTOM - IFRSDC, B.P. 171, Bobo-Dioulasso, BURKINA FASO.

3Present Address: 19 Bd de Port-Royal, 75013 Paris, FRANCE.

542 BULL SOC. VECPDR ECOL DECEMBER, 1987

ma = bites/man/night90

Rice Field80 —

1--- _..\Savanna

70 —

Downtown60 —

50 —

40-

20 — p•

10 — f • • =/

0I I I I I I I 11 F M A M J J A S O N D

10.0 — h = infective bites/man/night

1. 0 —

I.•• 1

l0. 1 — l:

C1

Cfig-

0.001 — I

o r Y 1J F M A M J J A S ON D

Figure 1. Annual variations of anopheline man-biting rate ( ma) and of malaria inoculation rate ( h) inthree sites surrounding the area of Bobo-Dioulasso, Burkina Faso.


of this species ( 0.5% after 8,000 dissections). regularly use bed nets. Malaria transmission may haveIn these conditions, malaria transmission was been reduced for this population for these reasons.

characterized by two factors: ( 1) it occurred in two Moreover, we have observed that the childhoodperiods during May and June then September to parasitological index followed the same pattern of theNovember, and ( 2) the yearly inoculation rate was 50 inoculation rates and decreased from the savanna to theinfected bites/man. urban area( Gazin et al. 1987). It is evident that malaria

infection can vary considerably within a small area ofThe urban area. Africa.

In the peri-urban district, Anopheles spp. werepresent from July to November only, with a high density REFERENCES CITEDin August ( 50 bites/man/night). Every inhabitant wastheoretically bitten 2,500 times by Anopheles per year Coz, J., H. Gnichet, G. Chauvet, and M. Coz. 1% 1.and 98 percent of these Anopheles were An. gambiae Estimation du taux de survie chez les Anopheles.s. l. Bull. Soc. Path. Exot. 54(6): 1353- 1358.

Parous rate was low ( 43%) and also so was the

sporozoite rate ( 0.19% after 500 dissections). Every Gazin, P., L. Ovazza, O. Brandicourt, and P. Carnevale.inhabitant was in theory bitten by 4.6 infected 1984. Etude parasitologique et serologique duAnopheles spp. per year. paludisme dans la region de Bobo-Dioulasso.

In the center of the city, Culex quinquefasciatus OCCGE-Inf. 92: 5- 14.was the major nuisance, with 25,000 bites/man/year.

Anopheles sl,p. were very rare and only A. gambiae Gazin, P., V. Robert, and P. Carnevale. 1985. Etudes. l. were caught with a density of 75 bites/man/year. longitudinale des indices paludologiques de deuxWe estimated the number of infected bites/man/year villages de la region de Bobo-Dioulasso ( Burkinaat 0. 15, corresponding to one infected bite every 7 Faso). Ann. Soc. Beige Med. Trop. 65(supl. 2):years. 181- 186.

CONCLUSION Gazin, P., V. Robert, and P. Carnevale. 1987. Le

paludisme urbain a Bobo-Dioulasso. 2. LesGreat differences appeared in the intensity and in indices parasitologiques. Cahiers ORSTOM, Ser.

the rhythm of malaria transmission in three sites located Entomol. Med. Parasitol. 25(2): ( In Press).within short distances.

The highest Anopheles spp. density was observed Robert, V., P. Gazin, C. Boudin, J.- F. Molez, V.in the rice field, while the highest transmission occurred Ouedraogo, and P. Carnevale. 1985. La trans-in the savanna. In the peri-urban district, transmission mission du paludisme en zone de savane arbor a etwas 50 times lower than in the savanna, and in the center en zone rizicole des environs de Bobo-Dioulasso.of the city it was 1, 000 times lower. Ann. Soc. Beige Med. Trop. 65(supl. 2): 201- 214.

In this region nobody is free from the risk of gettinginfected, even for the city inhabitants when considering Robert, V., P. Garin, V. Ouedraogo, and P. Carnevale.their frequent journeys to rural areas. 1986. Le paludisme urbain a Bobo-Dioulasso. 1.

Nuisance Culicidae in the city ( Culex Etude entomologique de la transmission. Cahiersquinquefasciatur) and in the rice field( Anopheles spp.) ORSTOM, Serie Entomol. Med. Paiasitol. 24(2):has encouraged a large proportion of the population to 121- 128.


CONTRIBUTIONS TO THE ECOLOGY OF TAHYNA VIRUS

IN CENTRAL EUROPE'

J. Pilaski2

ABSTRACT: Tahyna( TAH) virus is a mosquito-borne virus which is present in Eurasia where it causes a febrile

illness in humans, especially in children. The virus is transmitted transovarially in mosquitoes of the genus Aedes.The most important vectors are Aedes vexans and Aedes caspius. The virus could be isolated in 1981 from thesetwo species at the eastern shore of Lake Neusiedl in Austria( Ae. caspius) and at an inundation forest at the UpperRhine in Germany( Ae. vexans). The role of some ecological factors ( air and water temperature, time of inundation

process, salt content of the water) which influence the persistence of the virus within a natural focus is discussed.

RESUME: Tahyna( TAH) virus est un virus moustique-ne qui est present en Eurasie on it cause une maladie febriledans les hommes, surtout dans les enfants. Le virus est transmit transovariellement dans les moustiques du genreAedes. Les vecteurs les plus importants sont Aedes vexans et Aedes caspius. En 1981 it etait possible d' isoler levirus de ces deux especes stir la rive d' est de l' etang de Neusiedl en Autriche ( Ae. caspius) et dans une foretd' inondation de la partie superieur du cours du Rhin en Allemagne ( Ae. vexans). Le role de quelques facteurs

ecologiques( la temperature de l' air et de l' eau, le temps de l' evenement de l' inondation, la teneur en sel dans l' eau)qui influencent la persistance du virus dans le foyer naturel, est discute.

ZUSAMMP FASSUNG: Das Tahyna ( TAH) - Virus ist ein durnh Stechmucken iibertragenes Virus, welches in

Eurasien verbreitet ist and dort fieberhafte Erkrankungen bei Menschen, vor allem bei Kindem, hervornuft. Das

Virus wird transovariell in Miicken der Gattung Aedes ubertragen. Die wichtigsten Vektoren sind Aedes vexansand Aedes caspius. Im Jahre 1981 gelang die Vi usisolierung aus diesen beiden Stechmuckenarten im Bereich desOstufers des Neusiedler Sees in Osterreich( Ae. caspius) and im Oberrheingebiet in Deutschland( Ae. vexans). Die

Rolle einiger okologischer Faktoren ( Umgebungs- and Wassertemperatur, Zeitpunkt der Uberschwemmungen,Salzgehalt des Wassers), welche die Persistenz des Virus innerhalb eines Naturherdes beeinflussen, wird diskutiert

INTRODUCTION system illness in children living in Czechoslovakia havebeen caused by a TAH virus infection.

Isolation history and clinical symptoms:Tahyna( TAH) virus was isolated first in 1958 from Virus distribution in Eurasia:

Aedes vexans and Aedes caspius mosquitoes by To date, at least 15 natural foci of TAH virus exist

Bardos and Danielova( 1959) in the southeastern part of in Eurasia( Fig. 1), the most northern one in Finland atCzechoslovakia. It belongs to the California encepha- 69° of northern latitude( Traavik et al. 1978), the most

litis subgroup of the family Bunyaviridae( Bishop et al. southern one in Tajikistan, in the south of the Soviet

1980) and is pathogenic for humans. Human clinical Union at a latitude of 37° ( Daniyarov et al. 1974). In

cases caused by the virus have been found in Czecho- Germany, the presence of the virus was demonstrated inslovakia( Bardos et al. 1980), in France( Hannoun et al. 1968 and 1969 by direct isolation from Ae. vexans1969), and the Soviet Union (Lvov et al. 1972). The mosquitoes in the Upper Main region near Baunach

clinical picture of the illness in children is characterized ( Spieckermann and Ackerman 1972). The presence of

mainly by influenza-like symptoms. Bronchopneu- an additional natural focus was postulated in the Upper

monia has been found only in adults. It has been shown Rhine area near Worms on the basis of a seroconversion

by Bardos et al. ( 1980) that every seventieth case of of a sentinel rabbit in 1969 ( Spieckermann and

febrile illness and every fifth case of central nervous Ackemmann 1974).

Presented at the 1st European Branch Meeting, SOVE, Montpellier, FRANCE, 11- 12 September, 1986.

2Medizinisches Institut fir Umwelthygiene, Universitht Dusseldorf, 4000 Dusseldorf, FEDERAL REPUBLIC OFGERMANY.

DECEMBER, 1987 BULL SOC VECPOR ECOL 545

70 °n. lat. 47

65

60 47 -

55-

4530 _

51 34.

I 18------ _23

35—

10- 22

20

6 8— _

521

7 38. _ r_

451217—

27. 16

40 32

25• ? mow ? ammo?

35

7Q--}---rte , J , J ' A ' S ' 0 ' N , D

Figure 1. Seasonal distribution of Tahyna virus records in Eurasia between the 35th and the 70th latitude, compiledon the basis of literature statements. The study periods are marked by thin lines, the virus records by thicklines. The range between the 47th and the 48th latitude was extended without any respect to a correctscale ( Pilaski and Mackenstein, 1985).

Mosquito circadian rhythm: B. Upper Rhine area ( Gennersheim-Bingen): deadIn order to become acquainted with the circadian Rhine branches surrounded by meadows and

rhythm, mosquitoes were caught using a Moncadskij forests, which are inundated several times in thenet over 24 hours at the natural focus near Baunach on year by floods from the Rhine river( Fig. 4).29 and 30 August, 1980. The mosquito ( 90% Ae.

vexans) activity here had several peaks which were C. Upper Main area ( north of Bamberg, nearinfluenced by light intensity, the relative humidity of the Baunach): flat meadows and wooded slopes withinair, and by rainfall ( Fig. 2). the Main Valley, where inundations had occurred

during the last years.Virus isolation studies - 1980 and 1981:

In order to become acquainted with the ecological D. Lake Neusiedl ( eastern shore) in Austria steppeconditions within various mosquito habitats, especially and meadow biotopes with multiple shallow lakesin the natural TAH vines foci during two seasons, in and marshes ( Fig. 5).1980( January 2 to September 12) and 1981 ( August 17to September 10), the following six different regions in E. Isonzo River Delta in Northern Italy: corn fields

Germany, the Netherlands, Austria, and Italy were and meadows with partially dry ditches and withvisited ( Fig. 3). groves along the branches of the Isonzo River

Delta.A. Lower Rhine area( various sites): old cellars with

hibernating females; mixed forests, partially F. Amper Moos ( west of Munich): meadows and

marshy; rainwater basins where larvae were forests on the eastern bank of the small rivercollected. Amper.

546 BULL SOC VECPOR ECOL DECEMBER, 1987

A total of 45,705 mosquitoes belonging to 25 virus strain from an Ae. caspius pool in 1981 shows that

species was caught during these two seasons. The the virus still exists there.

results are given in TABLE 1. Altogether six TAH virus Since virus isolation from mosquitoes during onestrains were isolated, one from Ae. caspius mosquitoes season is often limited to only a few days, it is not

1 out of 148 pools), caught at the eastern shore of Lake possible from the limited data to answer the question

Neusiedl( Austria) on August 18, 1981. Five TAH virus whether the virus is still circulating within the naturalisolates derived from 62 pools ( 6,066 individuals) focus at the Isonzo River Delta ( Mackenstein and

caught in the Upper Rhine area( near Germersheim) on Pilasld 1982; Pilasld and Mackenstein 1983, 1985).

September 10, 1981, consisting of two isolates fromAntibody prevalence in humans in the Rhine

identified Ae. vexans mosquitoes and three fromarea:

unidentified mosquitoes. Between October 17, 1985 and June 1, 1986, a totalNo TAH virus strains could be isolated from of 1, 563 sera from hospitalized persons was collected

mosquitoes captured in the natural focus near Baunachfor a serological survey in the Rhine area between

in the Upper Main area Since the summer inundations Boppard in the north and Breicach in the south. TAHof the meadows had been stopped since 1978, it seems virus antibody titers were estimated by employing theobvious that this is no longer an important TAH vines indirect immunofluorescence assay ( IFA) using TAHfocus in Germany virus infected Vero B5 cells. As shown in Figure 6, the

Also, on the eastern shore of Lake Neusiedl in highest percentage( 23%) of positive sera was found inAustria the ecological conditions have changed since patients in the hospital of Germersheim near the Insel1965 when Aspock and Kunz ( 1967) had isolated the Griin, one of the major inundation forests in the Rhine

virus there. Nevertheless, the isolation of one TAH area.

I.

Yv e 16 t

1u. 1. 2(21.

INI L— I L1 U I I L_ J L___ 1 I I

11350000 171, i 1115000 1 1. 1

100MO: 1701: 1

woo90 77000 1 19 1.

1

11000 1 11

A ice'•

00 5500 j 18,. A v y7000 1 i. 11•

70 1400 1171,60 350 116 i.

175 1 1 1, %

50 11 1 15 i. 66 1 1,

40 22 ; 16;. 170,

icen 1.

30 5,5X13 i, .01. , ,, 111,

20 1, 6 1121.

10 0. 35 1111, 100.0, 17 I 1.

0 0. 08 1101_J 9f. i1\ 7l i a 11 O 3EZ

1: u.E70.

N. itE

S0.

1w.

catching site 31 ° n,

IMainauel i 71.u.

0

JJJ

17 11 19 70 71 77 73 76 1 7 3 6 5 6 7 1 9 10 11 17 13 16 15 % 17 11 n IEL

79. 01.5. 30. 01.10.

Figure 2. Circadian rhythm of mosquito activity between August 29 and 30, 1980, in the natural focus nearBaunach.


TABLE 1. Mosquitoes captured from January 2, 1980 to September 10, 1981, in Central Europe( Germany,Austria, and Italy) and isolated Tahyna virus strains.

o o 10000 ONON a 2 - 0

00 00VI

00 2 00 la.4

r 1 CV .` NM O a U i' K

Species n/% n/% n/% n/% n/% n/% n/% n/%

Aedes

annulipes 31/ 1cantons 299/ 10 3/< 1 28/< 1

caspius 3/< 1 41< 1 219/ 31 2511/ 91 4/ 1cataphylla 2/< 1cinereus 321/ 11 11/< 1 129/ 2 2/< 1 7/ 1 3/ 3 112/ 5communis 6/< 1 24/< 1darsalia 1/< 1excrucians 3/< 1flavescens 7/< 1geniculatus 1/< 1 7/< 1punctor 42/ 1 4/< 1refill 1/< 1

rossicus 1/< 1 73/ 2 51< 1 2/< 1 249/ 11sticticus 22/ 1 321/ 7 410/6 113/ 1 46/ 7 5/ 5 23/ 1vexais 10/< 1 4083/ 91 5877/90 1186/ 14 38/ 1 567/ 91 88/ 84 1827/ 832

Anopheles

claviger 2/< 1 2/< 1 3/< 1 1/< 1 1/ 1maculipennis 2/< 1 849/ 10 2/< 1 2/ 2plumbeus 71< 1 1/< 1 2/< 1

Culex

modestus 264/31 26/ 1pipiens 2057/ 72 1/< 1 12/< 1 724/ 9 146/ 5 5/ 5territans 6/< 1species 42/< 1

Culiseta

auudata 34/< 1 11/< 1 912/ 11 2/< 1subochrea 1/< 1

Mansonia

richiardii 27/ 1 1706/ 20 17/ 1

Ident. Females. 2859/ 100 4511/ 100 6506/ 100 8417/ 100 2744/ 100 625/ 100 104/ 100 2211/ 100Unident. Fern. 700 693 672 4 2241 1Total Females 2859 5211 7199 9089 2748 625 104 4452Total Males 195 150 1825 1034 31 7 19Unident. Mosq. 4244 6119 1595 2Ttl. Mosquitoes 3054 5361 7199 15158 9901 656 111 6066TAH Virus Str. 1 5MIR 0.07 0. 82

n= Number

Percentage of identified femalesMIR= Minimum infection rate per 1000 mosquitoes.1, 2= Number of isolated TAH virus strains.

548 BULL SOC. VECIOR ECOL DECEMBER, 1987

Ecological factors and TAH virus persistence: is required. The optimal temperature range is 28 to

Comparing the dates of preceding successful TAH 30°C. This explains why Ae. vexans appears rather latevirus isolations in Europe, it became obvious that a during the year ( Mohrig 1969; 158).water temperature above 16°C and an inundation The center of the TAH virus distribution in Europe

process occurring 40 to 50 days before mosquito lies within the Pannonian low plain. For this region a

catching am important ecological factors ( Mackenstein certain salt steppe or puszta is characteristic, which

1984). extends from Austria over southern Czechoslovakia to

These ecological conditions were found in the Hungary and Yugoslavia. For instance, the TAH virusRhine area in 1981. There was a significant drop in the focus in northern Yugoslavia described by Gligic andwater level of the Rhine after an inundation process Adamovic( 1976) lies within this region. According toduring the last week of July. The water temperature Bechtle( 1979), the origin of the high salt content of the

increased during the last week of July and the first week soil in this area are the sediments of the tertiary seaof August and dropped slowly until the end of In addition to Ae. vexans, another important vector

September. Thus, these dates fit into the above of TAH virus in Europe is Ae. caspius, a mosquito of

mentioned scheme. salt or brackish water ( Mohrig 1969). This mosquito

Oviposition by Ae. vexans females takes place not species is responsible for the TAH virus cycle in the salt

at the water surface but on the edge of slopes and the water meadows. Asptick and Kunz ( 1967) have found

mud of the river bed where inundations occur that TAH virus has been present in the steppe regions at

seasonally. The hatching rate of the larvae is increased the eastern shore of Lake Neusiedl in Austria in Ae.

after a dry season. It has been demonstrated under caspiur with high infection rates. The presence of TAH

experimental conditions that Ae. vexans larvae hatch at virus in two different ecological regions has been well

a water temperature between 14 and 16°C. For further documented in Austria, i.e., the puszta near Lake

development a water temperature of at least 16 to 17°C Neusiedl and the inundation forests of the Danube river

t_

s0 0

FrankfurtC

F®sMunchen Wien

Do

Q 200KmE

Trieste

Figure 3. Geographical position of the six regions( A-F 0) which had been studied in the time between September4, 1979, and September 10, 1981.

DECEMBER, 1987 BULL SOC VECIOR ECOL 549

N

41. :Do 1 km 114• 1••••

IMPoolI0 A

or " Ail ,0"-----,--"•...

NO , ^ A110. 1111. • ‘%* V n .-. •- n n n

Ili 13- mmLingenfeld A• 16.- 41/allialsr 1111110.„

t- •••• „ „ „

F -stat

applii IIII Inset GrunIt foist II 72- lb. , a.._ , ,, ,, • —... : 7

a _74._N. , 1- :_,.... 01111111111111111111111111111110",-,

41.Bell- Ilt 25/ 1981-141111111111111rheim if•r ANN

It ‘ o_ is,

IN11111, qi, •••--

411111111

411. 1111r)

41111111111r ,,

4111111P: ,

2 / 198041111W„24/ 1980 AIIII

t-•••- - • 1111. 11111 4111111111rt\ - 1%-

oNM%

11• 11111S' ilk

1411111d5h, to ' „...„,A A A

A A A An- Ilielhar

A A A AL 8"

1101:. #

n

A A A 1 NANn n n

n n n Germersheim f M 9

Figure 4. Map of the study region ( b) within the Insel Gran near Germersheim in the Upper Rhine area.

I.:

n

1 . .a, am

a••••

er,„.....47 Or

4777 r; N

7 0 1 2 3 4 5 krn CDr....;__-!... 0

ft?

si Andra

A

Ill,I• .

11. 11. . Oa _ 1. Onse•11/ OM

siedler 4,. -: -Ire. 4.-

A. 4iftenIllmitt ar . 41.--

513u

9 V, ,,7 g_ ti, --

7,-162 .

lieI

OhAIM! dna • .. S...

e --.-

IP

OM 1 -- -- -' Vit.1•••... II

IN• IMMO101 ,..., ~ II, M.

I • • Alkiii . 101• 1• 1• 1101• 11111•

411111,illirP••111• 91f1

1 Itn ....-....... 6. 1r:

s laIv A*.m.....-rsagt•

Ag 01lir m...._

Figure 5. Map of the study region ( D) at the eastern shore of Lake Neusiedl, Austria

550 BULL SOC. VECIDR ECOL DECEMBER, 1987

near Fischamend ( Aspock and Kunz 1966, 1967; species. For many decades it had been assumed thatAspbck et al. 1970). The question arises whether two mosquitoes are not able to transmit viruses

different TAH virus cycles exist in Europe, i.e., the transovarially. Peus ( 1966) stated that a virus cannot

cycle within the inundation forest, where Ae. vexans is arrange itself with a mosquito in order to form a virus

the main vector, and the cycle within the steppe region, reservoir. This opinion was in accordance with the

with Ae. caspius as the main vector. meaning of the whole scientific world. It was a kind ofThe question whether a virus transport takes place revolution when Watts et al. ( 1973) found transovarial

from one cycle to the other or whether the steppe or the transmission of LaCrosse virus in Aedes triseriatus. In

inundation forest cycle is of a greater relevance is no the following years transovarial transmission inlonger of interest since it is now clear that the virus can mosquitoes has been well-documented for manybe transmitted transovarially within one mosquito arboviruses ( Rosen, 1981). It has also been shown for

0 50 100kmI I

9°/ 01Boppard

St. Goar

3% 1 Eltville ( 11%)

I ngetheim ( 18°/ a) ' Gross- Gerau(6o/°)

KuhkopfAlzey •6%)

Inset Gr unGermershet m

23%)

Rastatt ( 11°/°)

7%)Ereisach

Figure 6. Prevalence of TAH virus IF antibodies in 1, 563 sera of patients admitted to 9 hospitals in the Rhine area.The two major inundation forests, Inset Grun and Kuhkopf, are indicated ( Neihaus, 1986).

DECEMBER, 1987 BULL SOC. VECIOR ECOL 551

TAH virus by Danielova and Ryba ( 1979). 820 l S/cm ( TABLE 2).We have been interested in the ecological factors In this table, also a recultivated brown coal mine

which are responsible for a successful transovarial near Most is included, which does not belong to any oftransmission of TAH virus. Danielova ( 1968) had the two mentioned virus cycles, i.e., the inundationshown that neural variants of TAH virus are less suited forest( Ae. vexans) and the steppe cycle( Ae. caspius).for propagation in the mosquito than extraneurally Czechoslovakian scientists isolated TAH virus in Junepassed strains. By experiments using neuroadapted and and July 1982 from the two mosquito species Ae.extraneurally passed strains for an artificial infection cantons and Ae. dorsalis. This was a surprise as virusof laboratory reared Ae. vexans mosquitoes, we found isolation from Ae. vexans was not successful( Malkovasome evidence that a neuroadapted TAH virus strain et al. 1984). In the surrounding area of Most manyreplicates poorly in the mosquito and that selection of mineral springs exist. A water sample taken onvariant ( or population) producing viremia in the mouse September 5, 1983, from a shallow pond in this regionor hamster correlates with enhanced ability to replicate revealed a conductivity of 47,000 µ S.in the mosquito ( Pilasld and Nelles 1983). A similar sample taken from a little soda pan at the

During mosquito catching activity in September eastern shore of Lake Neusiedl near Frauenkirehen on1981, we found the Greater Duckweed ( Spirodela August 27, 1983, revealed a conductivity of 26,000 MS.polyrrhiza) covering the surface of small water ponds in Thus, it may be tentatively postulated that thethe inundation wood at the isle Gdin. Visiting the same conductivity of the water where mosquito larvae hatcharea on September 13 and 14, 1982, it was recognized is an important ecological factor for the TAH virus cyclethat this little plant formed a large vegetation carpet within a natural focus.because the water level inside the inundation forest was Due to a low rainfall, a rather high air temperature,10 to 30 cm at this time. It seems to be a characteristic and the lack of further inundations during the weeksplant in inundation woods since it was also found in before our stay at the isle Griin, all water holes andother similar areas, i.e., inside the isle Kiihkopf north of ponds had a rather low water level. It is obvious thatisle Griin in October 1982, where Spieckermann and under these conditions many holes dry out The amountAckerman ( 1974) had postulated the existence of a of water inside a small pond is reduced in consequencenatural focus of TAH virus; in the Vojvodina in of the drying process. This may lead to an increase ofYugoslavia, where Gligic and Adamovic ( 1976) had the salt content and to a reduction of living space forisolated TAH virus from Ae. vexans mosquitoes; and in each mosquito larva. It has been shown that mosquitothe study area of Danielova near Dmholec in September larvae growing up under conditions of an1983. environmental stress" have a higher rate of virus

Pott ( 1980) demonstrated by estimating several infection than others, which live under optimalparameters of water chemistry that Spirodeletum ecological conditions ( Novak et al. 1986).polyrrhiza ( Kehldorfer 1915) is a well-documented Beaty et al. ( 1977) have demonstrated increasedplant community and is characterized by a conductivity hemagglutination activity for several viruses of therange of 480 to 650 pS/cm. Water samples taken from family Bunyaviridae due to high salt concentrations insmall water ponds and creeks at different TAH virus the diluent. The physicochemical mechanismnatural foci in Europe revealed a conductivity of 520 to responsible for this phenomenon is not known. It is also

TABLE 2. Conductivity of water samples taken in several natural TAH virus foci in Europe.

Date Country Locality Conductivity ( pS)

13./ 14. 09.82 Germany Isle Griin ( River Rhine) 600- 790

01. 10.82 Germany Isle Kiihkopf (River Rhine) 520- 630

09.08.82 Yugoslavia Vojvodina ( River Tisa) 820

01.09.83 Czechoslovakia Near Dmholec 520

05.09.83 Czechoslovakia Recultivated Brown Coal Mine 620


unknown whether this mechanism may be responsible Daniyarov, O. A., A. T. P. Pak, M. A. Kostyuk, V. P.

for the geographical distribution and the pathogenicity Bulyrev, T. M. Skortsova, L. L. Berezina, N. G.

of these viruses for mammals. Kondrashina, V. L. Gromashewski, and D. K.

Lvov. 1974. Isolation of Tahyna virus from

REFERENCES CITED mosquitoes in the settlement of Lower Pyandzh.

Southern Tajikistan. Ekol. Virusov. 2: 126- 129.

Aspock, H. and C. Kunz. 1966. Isolierung des Tahyna-Virus aus Stechmiicken in Osteireich. Arch. ges. Gligic, A. and Z. R. Adamovic. 1976. Isolation of

Virusforsch. 18: 8- 15. Tahyna virus from Aedes vexans mosquitoes in

Serbia. Microbiologija 13: 119- 129.

Aspock, H. and C. Kunz. 1967. Untersuchungen fiber

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Kindem. Padiatrie 19: 11- 23. Dusseldorf.

Beaty, B. J., R. E. Shope, and D. H. Clarke. 1977. Salt- Mackenstein, H. and J. Pilaski. 1982. Tahyna Virus

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Chumakov, S. Ya. Gaidamovich, C. Hannoun, D. Isolation of the Tahyna Virus. Cs. Epidemiol.

K. Lvov, I. D. Marshall, N. Oker-Blom, R. F. Mikmbiol. Immunol. 33: 88-96.

Petterson, J. S. Porterfield, P. K. Russel, R. E.

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Intervirology 14: 125- 143. Parasitol. Schriftenreihe, H. 18, VEB G. Fischer,

Jena.

Danielova, V. 1968. Penetration of the Tahyna virus to

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Bevolkerung des Rheingebietes. Medical

Danielova, V. and J. Ryba. 1979. Laboratory dissertation. University of Dusseldorf, indemonstration of transovarial transmission of preparation.

Tahyna virus in Aedes vexans and the role of this

mechanism in overwintering of the arbovirus. Fol. Novak, R. J. 1985. The effects of environmental stress

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Untersuchungen fiber Naturherde des Tahyna-

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Pflanzensoziologische and hydrochemische 1141.

BULL. SOC. VECTOR ECOL., 12( 2): 554- 560 DECEMBER, 1987

ESSAIS DE MODELISATION DE L'INGESTION

DES PARTICULES PAR LES LARVES DU COMPLEXE

SIMULIUM DAMNOSUM ( DIPTERA, SIMULIIDAE) 1

P. Elsen2

ABSTRACT: In the chemical control of simuliid larvae, the dosage of insecticide to be applied is empiricallycalculated without taking into account the alimentary behaviour of the larvae and different combinations of riversection and speed of current giving equal flows, which causes the passage of different quantities of insecticide perunit of river section and time. The author presents a new formula to calculate the quantity of insecticide to beapplied. The latter is based on the river section, the lethal dose of the product used, the number of particles per

unit of weight of the product, and on the speed of intake of particles by the larvae which is calculated as afunction of temperature, flux of natural particles in suspension in the river water, and the particle size and

relative quantities; the whole of this depending on the species considered. Applying experimental values to thismodel, for a given species, quantities of insecticide to be applied must be multiplied by a factor up to 1. 8 whenthe river section is doubled and the speed of current reduced in the same proportion( it will say the flow stays thesame). If different species are considered, the quantity to be used can be three times higher from one species toanother. These results were obtained with species of the Simulium damnosum complex in West Africa.

INTRODUCTION METHODE

Dans des travaux anterieurs ( Elouard et Elsen Dans une premiere etape, nous formulerons1977, Elsen et Hebrard 1979, Elsen 1980a), nous successivement les relations qui unissent la vitesse duavions montre que la vitesse du transit digestif des transit digestif aux divers parametres pris enlarves de S. damnosum s. l. vane en fonction du stade consideration ( stades larvaires, temperature,

larvaire, de la temperature de l'eau et de la concentration des particules, vitesse du courant).

concentration des particules en suspension passant par Dans une deuxieme etape, nous regrouperonsunite de temps. Nous avions egalement montre ces formulations en une equation permettant decomment calculer le temps necessaire pour la calculer le volume ingere par unite de temps.realisation d'un transit complet et calculer le volume La troisieme etape consistera d developper uningere par unite de temps ( Elsen 1980b). Nous modele a partir de cette nouvelle equation et de diversavions enfin etabli la proportion des particules en parametres complementaires( efficience de captage des

fonction de leur taille a la fois dans l'eau et dans le particules en fonction de leur taille, la dose letal pourtube digestif des larves ( Eisen 1979). Toutes ces l' insecticide concerne, le nombre de particules pardonnees vont nous foumir la base de la tentative de unite de poids du produit actif de cet insecticide, et lamodelisation que nous presentons dans ce travail. section de la riviere).

Nous avions d'autre part observe des differences Nous discuterons ensuite brievement le modelesensibles entre diverses especes du complexe( Eisen et ainsi obtenu a la lumiere des donnees experimentalesal. 1978), mais leur totale independance l'une par qui ont permis d'elaborer les equations de base.

rapport a l'autre oblige de regrouper les valeurs

obtenues pour chacune d'elles en une matrice a RESULTATSlaquelle on fera appel dans le cas dune programmation

du modele. Les parametres agissant sur l' ingestion.

1Presented at the 1st European Branch Meeting, SOVE, Montpellier, FRANCE, 11- 12 September, 1986.

2lnstitut de Medecine Tropicale Prince Leopold, Laboratoire d'Entomologie, 155 Nationalestraat, B- 2000Antwerpen, BELGIQUE.

DECEMBER, 1987 BULL. SOC. VECTOR ECOL. 555

a.- Le stade larvaire. Nous avons montre ( Eisen et Hebrard 1979)Rappelons que la vitesse absolue du transit que, en fonction de la temperature de l' eau et du flux

longueur reelle parcourue) presente des differences de particules, l'histogramme de la vitesse du transitpeu marquees entre les stades larvaires, mais qu'etant digestif se distribue dans un espace tridimensionneldonne la proportionalite de la taille des larves en sous la forme dune pyramide. Une analyse defonction de leur age, les jeunes larves manifestent regression multiple appliquee aux donnees nous aune vitesse relative du transit ( longueur relative fourni un plan de regression significativement correleparcourue) nettement plus rapide que celle des larves aux valeurs observees. L'expression generale de ceages (Eisen 1980a). L'expression mathematique de plan de regression est de la forme:

la courbe ainsi obtenue est la suivant

Lr = a+ b • T°= c • C 3)

Lri= a • Li- 13 1)

ou: T°= la temperature de l'eau en° C

dans laquelle: Lri = longueur relative du tube digestif

parcourue par le bol alimentaire C = le flux de particules par mm2 sec

pendant la duree de l'experience

chez les larves du stade i. On peut objecter dans cette equation que pour un

flux nul it existera malgre tout un transit digestif, ce

Li= longueur reelle du stade larvaire i. qui est illogique. De meme, a des temperatures

negatives croissantes, on finit par obtenir une valeur

a et B= deux constantes qui varient en negative du transit, ce qui est tout aussi illogique.fonction des parametres du Mais it va de soi qu'un flux nul ( courant nul ou eaumilieu ( voir§ suivant). distillee !) et des temperatures negatives ( glace) sont

des conditions incompatibles avec la vie des larves etLa courbe de cette relation indique une qu' il faut rester dans les conditions limites de leur

augmentation de la vitesse du transit digestif biotope. Le plan de regression defini ci- dessus nest

inversement proportionelle a Page du stade larvaire, applicable qu' a l' interieur de ces limites et, ainsic'est a dire a la taille des larves. La vitesse du transit considers, nous verrons que le modele s' accorde avec

varie done d'un stade larvaire a l' autre en fonction d'un nos observations. Ce plan de regression a ete definifacteur multiplicatif que l'on obtient par l'artifice pour le dernier stade larvaire.

mathematique suivant( rappelons qu' il y a sept stades L'aspect de pyramide evoque plus haut indiquelarvaires dont le septieme est le plus age): que les relations entre les parametres pris deux a deux

a • L•- B ne sont pas lineaires, mais ordonnees suivant deuxa • Li- B = ( a L7

B) ( pentes oposees, le point de rupture entre les deuxa • L7

Bpentes formant la zone du seuil. C' est ce que les

Le facteur multiplicatif vaut done: anglophones nomment" split lines" (= lignes brisees).

Afin d'effectuer une analyse de regression, il est dansa • Li- B Li - B

L7B

ce cas necessaire de transformer les variables. Perry2) ( 1982) propose d'utiliser les " variables factices" (=

a • L7-B

L7 Li dummy variables" des anglosaxons). Ces variables

s' obtiennent en considerant comme nulle la valeurb.- La temperature de l'eau et le flux de particules. observee situee au point de rupture des deux pentes, et

La concentration des particules en suspension en reevaluant les autres valeurs observees en lesdans l'eau est insuffisante en elle-meme car il faut diminuant de la valeur observee au point de rupture.tenir compte de ce que les larves vivent dans l'eau Nous avions, par exemple, observe un point decourante. La quantite des particules qui passeront rupture a 25° C qui prend des lors la valeur zero et lesdans leurs premandibules depend des lors a la fois du

autres temperatures sont reevaluees par soustraction denombre ( N) des particules par mm3 d'eau, c'est a dire

25, ce qui donne pour chaque pente ( en regard desla concentration en particules, et de la vitesse ( v) du

temperatures experimentees) les deux nouvelles seriescourant exprimee en mm/ sec. Cette quantite est le

de valeurs suivantes:flux (C) des particules par mm2 de section de riviere

surface approximative des premandibules) T° 10° C 15° C 20° C 25° C 30°C 35° Cequivalant a: T1°: - 15 - 10 - 5 0 0 0

C= N vT2°: 0 0 0 0 5 10

556 BULL. SOC. VECTOR ECOL. DECEMBER, 1987

T1° et T2° sont les variables factices pour les et oil L represente la longueur moyenne reelle du stadetemperatures. On procedera de meme pour les flux de larvaire considers et qui varie suivant l'especeparticules ( C) en obtenant deux nouvelles series C1 et incriminee. A partir de cette relation et de parametres

C2. En appliquant cette methode, 1' squation ( 3) du complementaires, nous allons progressivement stablir

plan de regression se transforme en: un mod8le qui devrait permettre de doser lesinsecticides de la facon la moms empirique possible.

Lr= a+ b • Ti° - c • T2°+ d• C1 - e• C2 ( 4)

Les parametres complementaires et leL'examen des relations ( 1) et ( 4) nous montre modele.

que pour une duree d'expsrimentation dsterminee, la

longueur relative parcourue par le bol alimentaire peut a.- L'ingestion des particules suivant leur taille.etre obtenue soft u partir de la longueur moyenne Nous avions déjà public ( Eisen 1979) lesreelle du stade larvaire considers pour des conditions proportions des tailles des particules rencontrses dansconstantes de temperature de l'eau et de flux de l' eau des rivieres et dans le contenu intestinal desparticules, soit pour un stade larvaire donne en differents stades larvaires de S. damnosum s. l. Nousmesurant ces deux parametres. le redonnons ici complete par l'efficience de captage

Si le plan courbe de la relation( 4) ne vane pas, des diverses categories de particules et qui s' obtient ensinon en amplitude, suivant les stades larvaires, on effectuant, pour chaque stade larvaire, le rapport entrepourrait imaginer de generaliser cette relation en y les proportions de particules rencontrses dans leurappliquant le facteur multiplicatif ( 2). Il s'agit tube digestif et les proportions correspondantescependant dune audace que nous sviterons en 1' absence rencontrees dans l'eau ( TABLEAU 1). Ces rapportsde verification experimentale qu' il ne nous a pas ete nous font apparaitre deux phenomenes: dune part ladonnee de rsaliser. Rappelons cependant que dans la confirmation dune capacite de capture des grosseslutte chimique contre les larves de Simulies, c' est le particules qui augmente avec rage des larves, mais quistade 7 qui est le plus resistant. Des lors, dans son est neanmoins faible pour tous les stades, et d'autreutilisation pratique, le modele pourra etre simplifie en part une capacite de captage nettement plus elevsene considerant que ce seul stade 7, et comme la pour les particules comprises entre 4.7 et 9.4 µ m

relation ( 4) a ete etablie pour ce stade, le modele ne malgre leur nombre 6.5 fois moindre clans l'eau parsera pas mis en dsfaut par la generalisation proposee. rapport aux petites particules qui sont ingerees en

proportion egale u celle trouvse dans l'eau. LesLe volume ingere par unite de temps. raisons qui font que la dsficience de captage des

grosses particules soit compensse par une efficience

Le developpement mathematique aboutissant u plus grande au niveau de cette classe particuli8re dela relation qui permet de calculer le volume de matiere taille des particules plutot quune autre trouventingere par seconde a fait 1' objet d'un travail antsrieur vraisemblablement son origine dans la morphologieElsen 1980b). Nous n'y reviendrons done pas et des prsmandibules filtrantes et la dynamique des

rappelerons seulement qu'il est base sur le temps fluides i3 leur niveau. Il y aurait done inter& u ce quenecessaire pour rsaliser un transit complet ( T&, les insecticides particulaires soient formulss enexprims en secondes, qui vaut: fonction de cette categorie. Mais it faut tenir compte

de l' interfsrence avec la capture des autres categories de

Tc— 100 T 5) taille. Le probl8me peut etre resolu a partir du

5, 04457- 0,46295 Lr+ 0,03809 Lr2- 0, 00024 Lr3 TABLEAU 1.

On peut en effet en deduire le volume moyenet ou: T= temps, en secondes, utilise pour stablir la occups par chaque categorie de taille pour 100

relation( 4). particules capturees ( puisque 1' on traville avec des

pourcentages). Pour simplifier le calcul de leur

Lr= longueur relative parcourue par le bol ali- volume, nous postulerons que les particules sontmentaire et qui s' obtient par la relation( 4). spheriques, mais en sachant bien qu' elles ne le sont

pas clans la realits, ce qui leur permet de s'emboiterLe volume ingere par seconde s' obtient comme suit: clans le tube digestif et d'en occuper quasi 100 pour-

cent du volume. Pour chaque categoric nous

V— 0,002124 L3

3 6) prendrons en consideration le diametre moyen. Les

Tc volumes ainsi obtenus peuvent etre ensuite assignesdune valeur relative par rapport au volume total des


100 particules ( TABLEAU 2). Ces valeurs sont bien ou Ai represente le pourcentages de V occupe par lessur tits approximatives, mais ce qui compte ici est le particules de taille i, ce qui explique la valeur 100 auraisonnement qui mene a la forme theorique du denominateur. En divisant ce volume par celui ( Wi)mod8le. A partir de ces valeurs et de celles obtenues de une particule de taille i, nous aurons le nombre depar la relation ( 6), on pourra deduire le volume reel particules i reellement ingerees par seconde:ingere pour une categoric de taille donnee. Commeles volumes indiques au TABLEAU 2 sont exprimes 109• V • Ai 7)en µ m3, it faut multiplier le volume V de la relation

100 Wi6) par 109. La fraction du volume ingere ( V)

occ3pee par les particules de taille i vaut donc ( en

Ceci est capital pour un dosage d'insecticideparticulaire, comme par exemple le Bacillus

109 • V • Ai thuringiensis H-14, une fois que 1' on connait la dose

100 letale du produit utilise, c'est a dire le nombre

TABLEAU 1. Les proportions des tallies des particules dans 1' eau de riviere et dans le contenu intestinal desdifferents stades larvaires de Simulium damnosum s. l. et leur efficience de captage ( EC) par ceslarves( Danangoro. mars 1977. Cote d' Ivoire).

Tailles des Eau de Stades larvaires

particules riviere VII VI V IV III II

enµ m. % % EC % EC % EC % EC % EC % EC

1. 0 x 4.7 73. 68 74. 18 1. 01 74. 16 1. 01 75. 26 1. 02 76.53 1. 04 79.87 1. 08 82. 11 1. 11

4.7 x 9. 4 1122 14.84 1. 32 14.59 1. 30 13. 74 1. 22 15. 31 1. 36 15.78 1. 41 15. 67 1. 40

9.4 x 23. 6 728 7.42 1. 02 8. 07 1. 11 7. 69 1. 06 6.90 0.95 4.08 0.56 2. 10 0. 29

23.6 x 47. 2 4.92 2.08 0.42 1. 82 0.37 2.04 0.41 0.79 0. 16 0.27 0.05 0. 12 0.02

47.2 2.90 1. 48 0.51 1. 36 0.47 1. 27 0.44 0.47 0. 16 - -

TABLEAU 2. Volume ( V) par stade larvaire de chaque categoric de particule ingeree en fonction de leur

proportion( extrapolation du TABLEAU 1) et leur pourcentage correspondant du volume total desparticules ingerees.

Volume moyen

enµ m3) de une Stades larvaires

particule dans VII VI V IV III II

chaque categorie V % V % V % V % V % V %

6.8 504 0.24 504 0.26 512 0.27 520 0.64 543 2. 81 558 5.00

183. 5 2722 1. 32 2677 1. 41 2521 1. 35 2809 3.45 2895' 15. 00 2875 25.76

2352.0 17452 8.46 18981 9.96 18087 9. 71 16229 19.92 9596 49. 71 4939 44.26

23227. 8 48314 23.43 42275 22. 19 47385 25.44 18350 2252 6272 32.48 2787 24.98

95693. 2 137186 66.54 126073 66. 17 117720 63.21 43566 53.47 - -

558 BULL. SOC. VECTOR ECOL. DECEMBER. 1987

minimal de particules qu'une larve doit ingerer pour simplification, est la suivante:

mourir. Nous y reviendrons un peu plus loin.On peut d'autre part obtenir le nombre de 47080,98 • T • M • Bi • Wi • N • S • v ( 10)

particules de taille i passant par seconde dans une Q—Ai • Z• L3•( 5,04457- 0,46295 Li.+0,03809 L,2-0, 000241. 3)

section de 1 mm2 de la riviere par la relation:

N Bi v 8) Dans ce modele, it n'y a que quatre parametres dmesurer:

100

ou : N= nombre total de particules dans 1 mm3 d'eaule nombre de particules( N) par mm3 d'eau.

la temperature( T ) de l'eau en C.de riviere. la section( S) de la riviere en m2.

Bi= pourcentages de N occupe par les particulesla vitesse( v) du courant en m/sec.

i.A partir desquels se deduit le flux de particules ( C=

v= vitesse du courant en mm/sec. N • v). Tout le reste constitue une constante qui

depend u la fois de l' espece consideree( L) et du produit

En divisant la relation ( 8) par la relation ( 7) nous utilise ( M ).obtenons le nombre de particules i devant passer par

seconde dans une section de 1 mm2 pour qu'une

particule i soit ingeree apres une seconde: DISCUSSION

N• Bi • Wi • v 9) Dans cette nouvelle formule, nous voyons qua

109 V Aidebit egal et pour une meme turbidite, la quantite

obtenue va changer en fonction de la vitesse du

b. Autres parametres. courant qui intervient egalement au denominateur dans

le calcul de la longueur relative parcourue par le bol

Si i represente la categorie de taille des alimentaire. Or, pour un meme debit de la riviere, la

particules de l' insecticide choisi, pour qu'un epandage quantite d' insecticide qui va passer par unite de section

de cet insecticide soit efficace, it faut que la relation de la riviere variera considerablement en fonction du

9) soit multipliee par la dose letale( M) pour obtenir jeu croise de la vitesse du courant et de la section

la quantite( q) de particules devant passer par seconde totale de la riviere. Par exemple, si l'on considere

dans une section de 1 mm2 pour que M soit ingeree dune part une section de 1 m2 et une vitesse de

pendant cette seconde: courant de 1 m/sec, et d'autre part une section de 2 m2

et une vitesse de courant de 0.5 m/sec, le debit sera le

M • N • Bi • Wi • v particules d'insecticide/ meme, mais la quantite d'eau, par consequent

q109 V •• A sec. mm2 d' insecticide, passant par unite de section vane dans ce

cas-ci du simple au double!

Le modele n'est encore que theorique en ce sensEn exprimant la vitesse du courant en m/ sec et en

que les coefficients reels restent encore u calculer.tenant compte dune part de la quantite ( Z) de

Mais en y appliquant les valeurs experimentales queparticules dans 1 mg de produit actif et d'autre part de

nous avons obtenues et en nous referant u lala section ( S) en m2 de la riviere, nous obtenons la

constatation faite ci- dessus, nous obtenons, suivantquantite de produit actif( Q u deverser dans la riviere

1' espece, une valeur de 1. 4 u 1. 8 fois plus elevee pourpour que la dose letale soit ingeree apres une seconde

une section de 2 m2 et une vitesse de 0.5 m/sec quede passage:

pour une section de 1 m2 et une vitesse de 1 m/sec.

Ceci indique que le dosage doit se faire au niveau de laM • Bi • Wi • N • S• v

section la plus large de la riviere.Q mg.•

Z• Vg.

Daautre part, u meme debit, plus la vitesse du

courant est elevee, plus les valeurs obtenues s' ecartent

ou V depend de l'espece consideree et est calcule en fonction de l'espece. Le jeu croise de ces resultatssuivant la relation ( 6) apres y avoir remplace Te par montre que si, a mime debit, on calcule la valeur de

la relation ( 5) et Lr par la relation ( 4). Pour Q dune part pour l'espece u ingestion la plus rapidesimplifier l'ecriture, nous conserverons l'abreviation dans le courant le plus rapide, et d'autre par pour

Lr. Des lors, l'expression finale du modele, apres l'espece la plus lente dans le courant le plus lent,


nous obtenons des valeurs qui vont du simple au du complexe Simulium damnosum ( Diptera,triple! Simuliidae) en Afrique de 1' Ouest. IV.

Ceci peut parraitre effrayant, mais it ne faut pas Consequences des variations observees sur leoublier que dans le calcul exposé ici, le facteur de temps dun transit complet et le volume ingerepollee n' intervient pas. Or ce facteur systematique- par unite de temps. Ann. Soc. beige Med. trop.ment utilise dans les epandages operationnels 60(2): 213-222.multiplie allegrement la valeur calculee par 600! ( 10

minutes, ou 600 secondes), ce qui est considerable- Elsen, P. and G. Hebrard. 1979. Le transit intestinalment superieur au triple mentionne ci-dessus. Ce chez les larves du complexe Simuliumfait, joint au calcul empirique de la dose letale, damnosum ( Diptera, Simuliidae) en Afrique demasque inevitablement les imprecisions du calcul de 1' Ouest. II. Influence de la temperature de l'eau,base applique au point d'epandage. de la concentration des particules en suspension

Faut- il rappeler que dans les Vosges en France, et de la nature de ces particules. Ann. Soc.le dosage applique en Afrique Occidentale a dii etre beige Med. trop. 59( 1): 49-58.triple pour obtenir un effet positif ( Noirtin et al.

1981) et que Von rencontre actuellement les memes Elsen, P., D. Quillevere, and G. Hebrard. 1978. Leproblemes en Belgique( donnees non publiees). Or it transit intestinal chez les larves du complexes' agit d'autres especes et d'autres conditions qui Simulium damnosum ( Diptera, Simuliidae) enconferment ce que nous venons d'exposer. Il est donc Afrique de 1' Ouest. I. Influence du sexe et deimperieux de tenir compte de ces parametres dans le l'espece. Ann. Soc. beige Med. trop. 58( 3):calcul d'un dosage et de poursuivre les recherches 209-217.

fondamentales plutot que de tlitonner par tests

empiriques successifs avant d'aboutir a un resultat. Guillet, P., J. M. Hougard, J. Doannio, H. Escaffre,

Precisons enfin qu' il reste plusieurs parametres a and J. Duval. 1985a. Evaluation de la

etudier et que ceux abordes ici ne constituent qu'une sensibilite des larves du complexe Simulium

premiere approche du probl8me en faisant apparaitre, damnosum a la toxine de Bacillus thuringiensis

nous l'esperons, la necessite dune telle approche dont H- 14. I. Methodologie. Cah. ORSTOM, ser.

les recents resultats appliques obtenus par Guillet et Ent. med. Parasitol. 23( 4): 241- 250.

al. ( 1985a, b, c, d) en Cote d'Ivoire sont une belle

illustration. Guillett, P., J. M. Hougard, J. Doannio, H. Escaffre,

and J. Duval. 1985b. Evaluation de laREFERENCES CITED sensibilite des larves du complexe Simulium

damnosum a la toxine de Bacillus thuringiensis

Elouard, J. M. and P. Elsen. 1977. Variations de H- 14. 2. Sensibilite relative de quelques

1' absorption des particules alimentaires et de la groupes d'especes et possibilites d'utilisation de

vitesse du transit digestif en fonction de certains doses diagnostiques. Cah. ORSTOM, ser. Ent.

parametres du milieu chez les larves de med. Parasitol. 23( 4): 251- 255.

Simulium damnosum Theobald, 1903 ( Diptera,

Simuliidae). Cah. ORSTOM, ser. Ent. med. Guillet, P., H. Escaffre, J. M. Prud'hom, and S.

Parasitol. 15( 1): 29-39. Bakayoko. 1985c. Etude des facteurs

conditionnant l'efficacite des preparations a base

Eisen, P. 1979. La nature et la taille des particules de Bacillus thuringiensis H- 14 vis-à- vis des

ingerees par les larves du complexe Simulium larves du complexe Simulium damnosum

damnosum dans les rivieres de la Cote d' Ivoire. Diptera, Simuliidae). 1. Influence de la nature

Rev. Zool. afr. 93( 2): 476-484. et de la taille des particules. Cah. ORSTOM,

ser. Ent. med. Parasitol. 23( 4): 257-264.

Elsen, P. 1980a. Le transit intestinal chez les larves

du complexe Simulium damnosum ( Diptera, Guillet, P., H. Escaffre, J. M. Prud'hom, and S.

Simuliidae) en Afrique de 1' Ouest. III. Bakayoko. 1985d. Etude des facteurs

Influence du stade larvaire, du nycthemere et de conditionnant 1' efficacite des preparations a base

la saison. Ann. Soc. beige Med. trop. 60( 2): de Bacillus thuringiensis H-14 vis-à-vis des

203- 212. larves du complexe Simulium damnosum

Diptera, Simuliidae). 2. Influence du temps de

Elsen, P. 1980b. Le transit intestinal chez les larves contact et de la quantite de particules naturelles

560 BULL. SOC. VECTOR ECOL. DECEMBER. 1987

en suspension clans l'eau. Cah. ORSTOM, sdr. Vosges: les origins de leur pullulation et les

Ent. med. Parasitol. 23(4): 265- 271. mdthodes de lutte. Cah. ORSTOM, sdr. Ent.

med. Parasitol. 19( 2): 101- 112.

Noirtin, C., B. Boiteux, P. Guillet, C. Dejoux, F.Beaucournu-Saguez, and J. Mouchet. 1981. Perry, J. N. 1982. Fitting split- lines to ecologicalLes simulies, nuisance pour le bdtail dans les data. Ecol. Entomol. 7: 421-435.

BULL SOC. VECTOR ECOL, 12(2): 561- 563 DECEMBER, 1987

IMPORTANCE OF VECTOR OVERWINTERING TO DISEASE MAINTENANCE'

W. C. Reeves2

When I was asked to discuss the importance of than a transovarian mechanism would be ruled out."vector overwintering to disease maintenance, my first This statement anticipated the basic question that stillthought was that the answer was simple. If a pathogen concerns us today— how do arboviruses overwinter oris endemic in an area and is dependent on a vector for its survive any period adverse to their continuousmaintenance, the vector must survive adverse periods or transmission?

the pathogen will disappear. However, on further It is quite clear that the endemic persistence of anconsideration I realized that a number of vector-borne arbovirus in any area is threatened annually bypathogens can survive for long periods as chronic circumstances that may interrupt continuousinfections in a vertebrate host and in the absence of a transmission. In temperate areas in the winter,vector. shortened daylight hours and low temperatures

It seemed logical then to consider how mosquitoes inactivate the vector population to a degree thatsurvive periods unfavorable to their continuous and precludes continuous virus transmission. In sub-rapid reproduction. Again, the answer was relatively tropical and tropical regions, prolonged dry or rainysimple. Mosquitoes survive low or high temperatures seasons also may disrupt transmission. In both

and droughts as long living adults, eggs, larvae, or temperate and tropical regions, prolonged drought or

pupae. Their life table has to be extended sufficiently to effective vector control programs also can interrupt

assure that a nucleus population will survive and that transmission. However, in spite of such disruptions,

subsequent generations will develop when conditions some arboviruses seem to persist as endemic infections

are favorable. If this is not accomplished, the species in many regions of the world.will disappear until it is reintroduced along with any The principle hypotheses that have been advanced

virus that is dependent on the vector. to explain the survival of mosquito-borne arboviruses

At this point I decided I must again face head on the in temperate areas through adverse periods and their

question that has plagued researchers for many years. reappearance under favorable circumstances are:How do arthropod-bome pathogens survive periods

adverse to their continuous transmission? In the interest 1. The virus survives in diapausing adult femaleof time I am going to limit my further considerations to mosquitoes that are the primary vectors in thethe mosquito-borne arboviruses although my thoughts summer. Females feed on an infected vertebratewill apply to many other vector-borne pathogens. host in the fall, survive the adverse period, and

To my knowledge, the first statement that retain their ability to transmit infection by biteaddressed the problem of virus survival was made in and reinitiate serial transmission under favorable1945. Hammon, Reeves, and Galindo were concerned circumstances.

with the overwinter relationships of western equine

encephalomyelitis and Si Louis encephalitis viruses to 2. The virus persists in the vector population byhibernating Culex tarsalis. This species was the newly transovarial transmission. Any life stage of thediscovered primary vector of these diseases in the vector that survives an unfavorable period

western United States. They stated," Unfortunately, we may carry the agent until conditions favordo not know whether the chances of this species serial transmission between vectors and

surviving the hibernation period are decreased by vertebrate hosts. This concept infers that the

having had a blood meal or whether survival is virus is a commensal parasite in the vector

dependent on such a meal. If the former is the case, that has become partially adapted to vertebratewinter carry over in the mosquito vector by any other hosts.

Presented at the 18th Annual Conference of the Society of Vector Ecologists, University of California, Riverside,November 20, 1986.

2Department of Biomedical and Environmental Health Sciences, School of Public Health, University of California,Berkeley, California 94720 U.S A.


3. The virus persists as a chronic infection in the efficient type of cycle are La Crosse, California, and

organs of vertebrate hosts and periodically Rift Valley fever viruses that are transmitted by Aedesreappears in the blood where it can be a source for mosquitoes. Eggs of these vectors survive cold winter

renewed infection of a vector population. periods or prolonged dry periods. J arge broods of

potentially infected mosquitoes emerge once4. The virus does not remain in what appears to be environmental conditions release the eggs from

endemic areas but actually is reintroduced diapause in the spring or summer. Prototype Californiaannually or at longer intervals by migratory or encephalitis virus survived for eight months in infected

vagrant vertebrate hosts or vectors that come Aedes eggs even when they were repeatedly frozen andfrom areas where transmission is more thawed before hatching.continuous. A most interesting alternative pattern for a

California group virus is just now emerging. The JenyOther hypotheses have been advanced but to me the Slough variety of Jamestown Canyon virus has Culiseta

most plausible are the four above. In each of these inornata as its vector in California In most of

alternatives, the virus persists in a mosquito vector or California this is a winter-time mosquito. The

vertebrate host species that has been infected during a population peaks in the winter and spring. The

period when conditions favored rapid serial passage. population survives the summer as females in a poorlyNext, I want to consider briefly the evidence in favor of defined aestivation. We are fmding that Jeny Slougheach hypothesis. virus is very efficiently transmitted transovarially and

There is some evidence that virus can persist in the virus probably survives the adverse summer periodfemale mosquitoes that have taken a prewinter blood in a few quiescent females. It is hypothesized that thesemeal. Virus has been isolated from adult female females can transmit virus by bite late in the fall and thatmosquitoes collected in mid-winter. In addition, their progeny are infected transovarially.individual experimentally infected female mosquitoes The third alternative is that virus overwinters inhave retained infection when held at outdoor chronically infected vertebrate hosts that can be sourcestemperatures for over eight months, including a winter of vector infection. Western equine encephalomyelitisperiod. However, few virus isolations have been made virus can persist in organs of birds for up to 10 monthsfrom overwintering female mosquitoes and most and we have recovered virus from naturally infectedstudies of such populations have indicated that most hosts in mid-winter. However, we have not been able to

diapausing females have not had a prewinter blood meal infect vectors on chronically infected birds, so theand do not undergo gonotrophic dissociation. question still is, can a vector become infected by feeding

To turn to the second alternative, evidence is on such hosts?

rapidly accumulating that transovarial infection of I will not discuss the probability that viruses aremany viruses in their vectors is more common than was reintroduced annually to areas where infectionbelieved previously. There is evidence that at least 50 disappears in the winter. Data are very fragmentary inarbovinuses can have some degree of transovarial spite of extensive efforts to trace movements of species

transmission. Important pathogens, such as yellow that are known hosts and that migrate great distancefever, dengue, Japanese B, St. Louis, Murray Valley, each year.

California, Ross River, Rift Valley, sandfly fever, andvesicular stomatitis viruses are in this group. SUMMARY

Interestingly, the rate of transovarial transmission ofmost agents does not seem to be sufficient to consider In summarizing the relationships of vectorthat this mechanism alone will allow virus survival for overwintering to arbovirus maintenance, I am going tomultiple generations without amplification in a assume that there are at least three classes ofvertebrate host. However, it would suffice for arboviruses. In the first class, transovarial transmissionoverwinter survival. In the most efficient cases, 90 of virus in the vector represents the basic maintenancepercent or more of progeny from infected females are cycle. If a virus is endemic in a temperate area and isinfected. In addition, a portion of female progeny from transmitted by Aedes mosquitoes, it must fall into thisinfected females can transmit virus when they take their class as overwintering of most Aedes is in the eggfast blood meal after emergence and male progeny can stage.

transmit infection sexually to uninfected females. The second class is arbovinuses transmitted byExtrinsic incubation is completed during the larval and Culex mosquitoes. In this instance the primary modepupal stages. Some outstanding examples of this of overwintering is in diapausing adult females. Virus

DECEMBER, 1987 BULL SOC. VECTOR ECOL. 563

may overwinter transovarially or persist in infected reintroduction of virus to an area. In this instance,females that feed on a virus source prewinter. Culiseta vectors still must survive the winter and be available tomosquitoes also fall into this pattern except for the be infected in the spring or early summer or virusreversal of the season of adult mosquito activity in transmission will not occur.

regions with high summer temperatures. The following speakers will expand on theThe third class represents arboviruses that do not mechanisms for overwintering of four major genera of

utilise overwintering vectors but depend on chronic mosquitoes. This information is critical to ourinfection in vertebrate hosts for overwintering or for understanding of pathogen maintenance.

BULL SOC. VECIDR ECOL, 12(2): 564-567 DECEMBER, 1987

THE FUTURE STATUS OF ARBOVIRUSES IN NORTH AMERICA'

W. C. Reeves2

When Gil Challet invited me to participate in this the encephalitis viruses developed very rapidly in thecolloquium, he asked me to address three questions 1940' s. Primary vectors, such as Culex tarsalis andconcerning the future importance of diseases caused by Culex pipiens were identified and control programsarboviruses. These questions were: developed that targeted these species. It was found that

inapparent infections in wild birds were the primary1. Will the diseases that concern us today still be sources of vector infection. Infection and clinical

important in the future? disease in humans and most domestic mammals wasaccidental and of no importance as a source of vector

2. Will new arboviruses be shown to pose public infection.

health problems? In the 1940' s, California encephalitis and Colorado

tick fever viruses were discovered and associated with3. Will we address the control of arbovirus diseases human diseases. Since 1950, another 51 arboviruses

as we do now or use new approaches? were discovered in North America but only two, LaCrosse and Jamestown Canyon viruses, are frequent

He did not specify the geographical area to be causes of disease in man. These two viruses utilizeencompassed and I assume he did not want my remarks small mammals as their principal hosts and Aedes orto be restricted to Orange County, California Culiseta mosquitoes as vectors.

In response to the above questions, I will give you Today, 58 of the 504 arboviruses that occur in thea brief background about the arboviral diseases of world are known to be endemic in North America andpublic health importance that concern us in North few have been associated with a significant number ofAmerica today. I will then attempt to make some cases of disease in humans. This brief review hasreasonable predictions of what could evolve in the next illustrated the rapid development of knowledge on15 to 20 years and discuss some specific problems we arboviruses and their associated diseases in this century.must face. I will focus this discussion on viruses that

have been associated with human diseases. Predictions regarding the activity of endemicviruses

Historical Background Let me turn now to the diseases that we knowOur knowledge of arboviruses associated with considerable about— WEE, FFF, SLE, the California

human disease has largely evolved since 1930. In 1930, encephalitis complex, and Colorado tick fever. I must

only six viruses that infect vertebrate hosts and are predict that these viruses ' will continue to appear

transmitted by arthropods had been isolated in the annually in their endemic areas as sporadic cases andworld. Yellow fever was the only one associated with periodically as epidemics in both rural and urbanhuman infections and the other five viruses were populations. I do not believe that any of these infectionsimportant pathogens of domestic animals ( Blue tongue, will disappear in the foreseeable future. Each virusAfrican swine fever, Nairobi sheep disease, Louping ill, seems to be firmly imbedded over extensive areas in aand vesicular stomatitis). From 1930 to 1940, only nine silent cycle between vectors and wildlife hosts. In someadditional arboviruses were discovered and three of instances there is transovarial transmission of infectionthese— western equine encephalomyelitis ( WEE), in the vector populations, which provides a mosteastern equine encephalomyelitis ( EEE), and St. Louis efficient reservoir of infection. Eradication of theseencephalitis ( SLE)— were important pathogens of man cycles is impractical, economically unfeasible, andin North America Knowledge of the natural history of would require such drastic reductions of the vector and


2Department of Biomedical and Environmental Health Sciences, School of Public Health, University of California,Berkeley, California 94720, U.SA.

DECEMBER, 1987 BULL. SOC VECTOR ECOL 565

vertebrate host populations that it could even be and expensive task. However, it is the only way toundesirable. It also is impractical at this time to think rapidly control an epidemic that is in progress. Theseofprojects to immunize the wildlife hosts or to decrease infections have a very short season when they are activethe competence of vector populations through genetic and once clinical cases are identified, it can be assumedalterations. that many people already are infected. The exception to

The question inevitably arises Why not develop the above generalities about the possible value ofvaccines to protect humans from all of these diseases? vaccination and epidemic control are the exotic viruses,While this may be technically possible in today' s era of such as yellow fever, the dengues, and Ross River virusmolecular biology, the response is that it is impractical. in which humans develop a viremia sufficient to be aThe majority of these infections in man are inapparent source of infection for domestic and semi-domesticand the number of clinical cases in any area usually is vectors.

small. A very large number of persons would have to be A major problem in arbovirus research over thevaccinated at a high cost to prevent relatively few cases. past 50 years has been to determine how these agentsPublic health officials and the medical profession will survive the winter or are reintroduced each year intonot put a high priority on vaccination in anticipation of what appears to be endemic areas. Demonstration ofpossible future epidemics although once an epidemic is transovarial transmission of the California virus

occurring, it creates a widespread concern, even panic. complex in these vectors has partially answered thisHowever, once an epidemic develops it is too late for a question. However, it remains to be answered for thevaccine to be effective. Any unvaccinated person living other major pathogens. So far, these studies have notin an endemic area still would be at risk of infection opened new avenues for virus surveillance or control.from the bites of infected vectors even if surrounded by It is surprising that more of the 58 arboviruses wevaccinated persons. In addition, vaccination of humans know are present in North America have not beenwill not have any effect on the basic maintenance cycle associated with illness. The vectors and wildlife hostsof these infections in wildlife. of many of these viruses have frequent contact with

From an economical viewpoint, I must conclude man. It also is of continuing interest that in the averagethat an effective program to keep vector populations at summer in the United States, 50 percent or more of thelow levels will provide the best protection against febrile illnesses that involve the central nervous systeminfection being transmitted to susceptible persons. in humans cannot be diagnosed by the best diagnostic

To summarize, I believe that endemic viruses, such laboratories. I suspect on epidemiological grounds thatas WEE, FFF, SLE, La Crosse, Jamestown Canyon, and some of these cases will be shown in the future to beColorado tick fever will remain as endemic infections caused by vector-borne viruses that already have beenfor the foreseeable future. We must learn to live with or will be isolated. Current efforts to associate thesethese infections by suppression of vector populations to types of illnesses with known arboviruses have beenthreshold levels where transmission to man will be rare. unsuccessful. I also anticipate that new techniques willThe only alternative is for individuals to avoid exposure lead to the isolation and identification of additionalto vectors in circumstances where suppression of vector viruses from arthropods and vertebrate hosts and eachpopulations is impractical. of these will have to be evaluated as potential pathogens

It should be possible to continue to suppress vector of man.

populations in urban and suburban areas to levels thatwill interrupt basic maintenance cycles between Exotic vectors and virusesvectors and animal hosts. This will require the An additional prediction is that exotic viruses andestablishment and maintenance of intensive vectors will be introduced into North America. I mustsurveillance systems to monitor climatic factors that remind you that there are 504 known arboviruses andfavor virus activity, vector populations, virus infection only 10 peeeent are endemic to our region. Tourists,

in vectors and maintenance hosts, and human cases. other travelers, and immigrants continue to have onsetsDetection of virus activity or potentially significant of exotic arbovirus diseases after their return to or entryvector populations in urban centers must be responded into North America. For the human pathogens, I wouldto immediately with an effective program to suppress list dengue, yellow fever, Venezuelan equinethe vector population to levels that will prevent or encephalomyelitis, Japanese B encephalitis, and Rossminimize human exposure. Control cannot depend on River viruses as some likely candiciatts. If such agentsthe recognition of epidemics and a fire-fighting are introduced and the infection becomes established inapproach to their control. Suppression of a large native vectors and hosts, control or eradication will bepopulation of infected adult vectors is a very difficult very difficult and expensive.


I also expect that exotic vectors will be introduced establish " green belts" that include aquaticand their eradication will be very difficult. The recent environments within urban areas. Such developmentsintroduction of Aedes albopictus into the continental are desirable but almost inevitably will serve as sourcesUnited States and its unrecognized and rapid spread of vector breeding and provide habitats attractive toover an extensive area illustrate what can happen with vertebrates that are hosts of arboviruses. Related to thismodem transportation and increased interstate and problem are current programs that plan to use reclaimed

international movement of products, such as used tires, waste water to create marshes and wildlife habitatsThe problem is out of hand before it is recognized. We adjacent to or near urban areas.

were fortunate in this instance that the introduced A fourth problem is the constant expansion of thevectors do not appear to have been infected with an urban-suburban area into agricultural or unimprovedexotic pathogen that was maintained transovarially in lands, which increases the exposure of residents tothe vector population. If that had occurred, it would vectors. A significant part of the problem has been thehave represented the immediate establishment of a establishment of senior citizen communities in ruralreservoir of infection that would spread to native areas. This development is a recognition of thevectors and vertebrates and become established increased aging and unique needs of that population.

However, from an epidemiological viewpoint, this canSocietal changes related to effective control of lead to an increased exposure of the age group that is thearboviruses. most susceptible to SLE.

I want to turn now to Gil Challet' s third question. A fifth problem is the increased difficulty ofWill we address the control of arboviruses as we do developing effective systems to dispose of solid wastes

now or use new approaches?" I believe we will continue from our society. Used tires and a wide range of metalto utilize the majority of our present chemical, and plastic containers provide a very attractive breedingbiological, and physical methods of control insofar as site for some mosquito species. Indiscriminate disposalthey are effective and the society we live in will allow of such items on roadsides, in yards, or in denselyit. However, to be successful, we are going to have to vegetated areas makes them particularly difficult to findeither develop new approaches to control or change the and control

attitude of our society. Let me illustrate this with some A sixth problem is the increasing number ofexamples of current problems that I believe will become persons that are utilizing wild-land habitats forworse unless some radical new approaches are recreational purposes. Such areas usually have nodeveloped for vector management that are acceptable to organized resource for vector control and many vector-the general public and lawmakers. borne diseases prevail in such habitats. It can be

In recent years, several developments have made expected that recreational exposures will result in anvector control increasingly difficult in urban and increased number of infections with Colorado tick feversuburban areas. The increasing size and density of and the encephalitis viruses.

human populations has been paralleled by an aging, A seventh, and perhaps the most importantpoorly designed facility for disposal of waste water and problem, is the constantly increasing legal and socialsewage from such areas. Epidemics of St. Louis restrictions on the application of chemicals for vectorencephalitis in urban populations have reflected the control and on modification of environments for anyadaptation of Culex vectors to both underground and purpose. Simultaneous to this change in the socialsurface water disposal systems in urban areas as a major attitude, the genetic resistance of vector populations to

breeding site. It seems unlikely that the thousands of insecticides has developed more rapidly than themiles of present drainage facilities will be redesigned development of alternative and acceptable methods forand replaced in the near future. Control of vectors in management of vector populations. I see a possibilityunderground systems is and will continue to be difficult that pheromones and sugars may be used as effectiveand expensive. There is a need to redesign such baits for the attraction and control of vectors,facilities to exclude vectors or new chemical or particularly in urban environments. Very little researchbiological methods for control will have to be found that has been done on the pheromones of major diseaseare effective in such situations. vectors. Current research is showing that adults of

A second unsolved problem is the need to establish vector species, such as Cx tarsalis require one or moreeconomical and effective methods to dispose of sewage sugar meals daily. Use of these agents as attractants towithin reasonable distance of urban centers without a physical or chemical killing agent wouldproduction of vectors. revolutionize control programs. This is an area for a

A third problem is that our society wishes to major future research effort.

DECEMBER, 1987 BUIL SOC VECTOR ECOL 567

In summary, I can only anticipate that the problems. We cannot hope that old control methodsabove problems will not be resolved rapidly. I believe will be effective or acceptable in the future. A newthat vector populations will increase in many of generation of research and control workers will have tothe above environments in the future. This could develop new approaches. It may be that the mostlead to increased exposure of humans to the arbo- challenging problem that will face them is to find waysviruses. to alter social attitudes regarding environmental

modifications and legislation, particularly withConclusions. reference to actions based on feelings of vocal groups

I hope the above examples have illustrated why rather than on scientific facts. I cannot predict thenew approaches to control of vectors of arboviruses will probability of or timing when these challenges will behave to be developed rapidly to manage a variety of met.

BULL SOC VECTOR ECOL, 12(2): 568-579 DECEMBER, 1987

OVERWINTERING MECHANISMS OF NORTH AMERICAN CULISETA12

W. K Reisen3

ABSTRACT: The distribution and life history patterns of Culiseta species found in America, north of Mexico, werereviewed. Culiseta species were classified into four of the five possible categories using the Wesenberg-Lundsystem as modified by Frohne. The overwintering strategies of the arbovirus vectors, Culiseta melanura andCuliseta inornata, were described in detail. Culiseta melanura overwinters as larvae beneath root mats. All larvalstages are present during winter with development slowed by cold winter temperatures. Fourth instar larvae

accumulate during winter and pupate during spring, perhaps in response to breeding site enrichment by vernal runoffassociated with snow melt Culiseta inornata abundance patters vary with temperature, being summer active in thecolder northern latitudes and winter active in the warmer southern latitudes of its distribution. Females from

California remain reproductively active throughout the year and could not be induced experimentally to enterreproductive diapause. Flight and host-seeking activity is arrested by extremes in temperature during mid-summerand winter. Aestivation is preceded by the accumulation of hypertmphic fat without an associated reproductivedormancy.

Types of Dormancy. Distribution.

Because of confusion among the use of different The genus Culiseta consists of eight subgenera,

terms used to describe mosquito overwintering, it may which are distributed circumglobally. In North

be useful at the onset to briefly define some of the America, the genus is comprised of eight species, which

terminology which will be used in the present are grouped into three subgenera ( TABLE 2). The

discussion (TABLE 1). Dormancy may be initiated in distribution of all eight species is essentially temperate,response to either low ( hibernation) or high although the ranges of Cs. melanura and Cs. inornata

aestivation) temperatures, or in rare cases may not be extend to the most southerly portions of the Unitedrelated to temperature( athermopause). The intensity of States. Conversely, the distributions of Culisetathe dormancy and the degree of preparation required alaskaensis and Culiseta impatiens extend well north of

increases from quiescence through diapause. In the Arctic Circle.

immature mosquitoes, the intensity of the response isdifficult to define and often the stimuli required for Life Cycles.

termination are used to delineate the state achieved. In The occurrence of Culiseta species over a wide

adult female mosquitoes( males do not enter a dormant range of environmental conditions has led to the

state), the reproductive and/or digestive systems may evolution of a variety of life history or life cyclerespond to the environmental stimuli. In the far north, strategies. Wesenberg-Lund ( 1921) and Bates ( 1949)both systems usually respond with a complete arrest of classified temperate mosquito life history patterns intoreproductive activity and a suspension of both sugar and four types based on the number of generations per year

blood feeding. However, at warmer temperate and the mechanism by which the species survives thelatitudes, reproductive diapause may be achieved with adverse period(s). Frohne ( 1954) later expanded this

or without the suspension of carbohydrate feeding. classification to account for the unique life history

Text of a presentation in a Colloquium entitled," Overwintering in mosquitoes of medical importance," at the 18thAnnual Conference of the Society of Vector Ecologists, November 20, 1986, Riverside, CA.

2Funded, in part, by research grant AI-3028D from the National Institute of Allergy and Infectious Diseases,Biomedical Research Support Grant 5- S07-RR-05441 from the National Institutes of Health, and by special fundsfor mosquito research allocated annually through the Division of Agriculture and Natural Resources, Universityof California.

3Department of Biomedical and Environmental Health Sciences, School of Public Health, University of California,Berkeley, CA 94720, USA.

DECEMBER, 1987 BULL SOC VECPOR ECOL. 569

pattern of several Alaskan Culiseta. Members of the during summer in Texas after inundating the litter of drygenus Culiseta appear to exhibit four of the five possible tree holes. They also demonstrated that the egg raftslife cycles( TABLE 3). Some species, such as Culiseta could remain viable out of water for 72 hours under leafmorsitans and possibly Cs. inornata utilize more than litter. Further research is necessary, however, beforeone type of life cycle pattern. this mechanism can be accepted as an alternative to

None of the North American Culiseta species summer aestivation by the adult females. In California,were classified into Life cycle I, exemplified by Aedes gravid and parous females typically appear during latecinereus, which is univoltine and overwinters as summer and early fall before larvae or males can bediapausing eggs. found in nature. In addition, Cs. inornata most

Life cycle II, exemplified by Aedes caspius, is frequently oviposits in ground pools and rarely utilizescharacterized by multivoltine species, which survive artificial or natural containers.

adverse periods as diapausing, drought resistant eggs. Life cycle III, exemplified by Anopheles claviger,Marshall ( 1938) reported that in Europe Cs. morsitans is characterized by mosquitoes which overwinter asoverwinters as drought resistant eggs, which are laid hibernating larvae. Culiseta melanura exhibits this typesingly above the water line in tree holes. Conversely, of life cycle in the eastern United States, typicallyWallis and Whitman( 1968) found that in the laboratory overwintering in subterranean ground pools associatedthe American subspecies, Cs. morsitans dyari, with root mats.

oviposits egg rafts, which also are placed above the Life cycle IV, exemplified by Culer pipiens, iswater line. Morris et al. ( 1976) felt that in New York characterized by mosquitoes which are multivoltine andState Cs. morsitans overwintered as diapausing eggs, hibernate as adult females. Culiseta inornata iswhereas Siverly ( 1967) collected larvae during winter multivoltine and aestivates and/or hibernates as adultin Indiana. Apparently, if autumn is dry, the eggs will females, depending upon temperature. In the northernremain viable allowing overwintering in the egg stage; latitudes, Cs. inornata overwinters as hibernatinghowever, if the eggs are inundated by fall rains, they will females and is active throughout summer ( Hudson

hatch and the resulting larvae are capable of 1977), while in southern latitudes, Cs. inornata females

overwintering, thus, exhibiting the Type III life cycle. aestivate in summer and remain reproductively activeCertainly, a species which overwinters as drought during winter ( Barnard and Mulla 1978a). This

resistant eggs in the form of a raft is quite unique among remarkable plasticity will be considered in detail later inmosquitoes. this presentation.

Wilkins and Breland ( 1949) and Buxton and The collection of adult females prior to males orBreland( 1952) were able to recover Cs. inornata larvae larvae during spring indicates that Culiseta minnesotae

TABLE 1. Classification of mosquito dormancy( modified from Mansingh 1971).

HIBERNATION: AESTIVATION: ATHERMOPAUSE:

Any low temperature arrest Any high temperature arrest Arrest not related temperature

I IQUIESCENCE: OLIGOPAUSE: DIAPAUSE:

Unprepared response to short-term Partially prepared response to mild Prepared response to harsh and

adversity but long-lasting adversity long-lasting adversity

I I I

I IREPRODUCTIVE: METABOLIC:Follicles arrested at Stage I, Reduced blood and sugar feeding,reduced blood-feeding avidity survival dependent upon hyper-

throphic fat


TABLE 2. Distribution of the genus Culiseta in America north of Mexico ( summarized from Darsie andWard 1981).

Species Distribution

Subgenus Climacura

melanura ( Coquillett) Eastern United States

Subgenus Culicella

morsitans ( Theobald) Northern United States and Canadaminnesotae Barr Northern United States and Central Canada

Subgenus Culiseta

alaskaensis ( Ludlow) Rocky Mtns. of United States and Canadaimpatiens ( Walker) Northern United States and Canadaincidens ( Thomson) Western United States and Canadainornata ( Williston) United States and Western Canadaparticeps ( Adams) Pacific Coast of United States and Canada

and Culiseta incidens most likely overwinter as adult being held for more than two and a half months. Thisfemales. The early spring collection of female Cs. year-long female life cycle must certainly make theseminnesotae at light traps before the emergence of the Culiseta among the longest lived adult mosquitoes!first Cs. morsitans in Minnesota led Barr( 1957) to first

consider Cs. minnesotae as a distinct species. Overwintering by Culiseta melanura.In the hot, arid southwest, Cs. incidens and Cs. Because of their involvement with the

particeps most likely aestivate during summer, since transmission of arboviruses, Cs. melanura and Cs.

they are plentiful during fall and spring but essentially inornata are the best studied of the North Americandisappear from collections during summer, similar to Culiseta. Detailed studies of the overwintering biologyCs. inornata. Barr ( 1985), however, has collected egg of Culiseta melanura have been restricted to therafts of Cs. incidens during every month of the year in northeastern United States. Joseph and Bickley( 1969)coastal California, under the same photoperiod collected adults in Maryland from May throughregimens at which this species disappears in the Central October, but found all larval instars present throughout

Valley. These contrasting findings may indicate the the year ( FABLE 4). Although larval developmentimportance of temperature in the induction of appeared to be slowed by cold temperature, theaestivation. persistence of all instars suggested that development

Detailed studies of Culiseta in Alaska led Frohne progressed slowly throughout winter with the transition1954) to introduce a fifth mosquito life cycle, from L4 to pupa restricted to spring and summer. These

exemplified by Cs. impatiens. As described by Hopla results suggest a state of hibernation in larval quies-1970), Cs. impatiens and Cs. alaskaensis overwinter cence rather than in diapause. Wallis( 1953) found that

as females which have never imbibed a blood meal. the Fl progeny from females collected during autumnOverwintering females emerge during April and begin would pupate during December when reared underblood feeding while snow is still on the ground. warm laboratory conditions. Wallis did not consider

Oviposition occurs in May after snow melt. The photoperiod important because this species typicallyresulting larvae mature relatively rapidly and emerge overwinters in underground sites where photoperiod

during July and August, mate, feed on nectar, and then was unlikely to be perceived. The month long arrestedaestivate for the remainder of the summer. Males die growth achieved by fourth instar larvae reared onout, but the female progeny of the spring generation alfalfa pellets was attributed by Wallis( 1962) to dietaryenter an obligatory winter diapause, which is mandatory deficiencies, which were rectified by the addition offor the initiation of blood feeding the following spring. liver powder. In nature, the vernal thaw and associatedEven under warm laboratory conditions, Frohne ( 1953) runoff could add nutrients to breeding sites triggeringfound that females would refuse to blood feed until after pupation; however, carefully designed studies to verify

DECEMBER, 1987 BULL SOC. VECIDR ECOL 571

TABLE 3. Life cycles exhibited by the genus Culiseta in American north of Mexico.

Life Dormant CulisetaLife Cycle Type' Stage Period Species

I. Aedes cinereus none

II. Aedes caspius egg winter morsitans

summer inornata ??

III. Anopheles claviger larvae winter melanura

morsitans

IV. Culex pipiens females winter minnesotae

inornata

incidens

summer inornata

particeps ??

incidens

V. Culiseta impatiens females summer/winter impatiens

alaskaensis

Classification scheme after Wesenberg-Lund ( 1921) and Bates ( 1949) as modified byFrohne ( 1954).

TABLE 4. Seasonal abundance pattern of Culiseta melanura in Worchester County, Maryland, 1965-1966 ( from Joseph and Bickley 1969).

Months Egg 1st 2nd 3rd 4th Adult Adult

1965- 1966 Raft Instar Instar Instar Instar Pupa Males Females

JanuaryFebruaryMarch

April

MayJune

JulyAugust

September

October

November

December

Not Present, *= Few, **= Moderate, and*** = Abundant.


this hypothesis have not been performed Alter- diapause had been induced. Interestingly, a controlnatively, pupation could occur as a result of a faster group reared from L1 to adult at 12L and 10°C did notlarval feeding rate associated with warm spring enter diapause and matured follicles normally with a 10/temperatures. 2° follicular ratio= 2.72. The requirement for the abrupt

shift from 16L to 12L photoperiod to induce diapauseHibernation and Aestivation by Culiseta was difficult to interpret, since a similar photoperiodinornata. transition in nature would occur gradually over several

Considerable research effort has been expended months. The data of Dow et al.( 1976) in Weld County,describing both winter and summer dormancy in Cs. Colorado, suggested that a reproductive diapause mayinornata. In colder latitudes and higher altitudes, Cs. not be achieved in nature. Resting females collected ininornata is active during summer and hibernates as March were either porous or gravid, and emptyadult females in winter ( Hudson 1977a). Hudson nulliparous females could not be collected until May1977b) reared the Edmonton, Alberta laboratory strain when the Fl progeny of the overwintering cohort

of Cs. inornata from Ll to L4 under summer conditions pupated and emerged In contrast, the first Cuiexof 16L and 20°C and then transferred the larvae to the rarsali<s females concurrently collected during springexperimental regimens shown in Figure 1. When were typically empty or freshly blood-fed nullipars.transferred to a 12L photoperiod, oogenesis was In the Sacramento Valley of California, Meyer etarrested at stage I and the ratio of the primary to the al. ( 1982a) collected host-seeking female Cs. inornatasecondary follicle length was less than or slightly above from September through April with peak abundance1. 5 two weeks after emergence; significantly different occurring during fall (Fig. 2). Larvae first appeared infrom larvae allowed to pupate and emerge at 16L( Fig. October ( Meyer et al. 1982a,b).1). Temperature had little effect upon the induction of We have found a similar pattern in the southernthe diapause condition. Blood feeding avidity also was San Joaquin Valley with a dramatic decrease in theattenuated indicating that a reproductive winter abundance of host-seeking females at CO2 baited traps

3.5—

3. 0— 14- 15 Days —Days Postemergence

7- 8 Days

2.5— 1111111111111

111111111111

1. 5— 111111111111IIIIIIIIIIII

o ss

0.5—

A A 4,4 Ad A.0.0

Temp(° C) = 10 15 20 10 15 20

Hours L:D= 12: 12 16:8

Figure 1. Mean primary/secondary follicular length ratios for Culiseta inornata females ( Edmontonlaboratory colony) 7-8 days and 14- 15 days postemergence. Females were reared from ecolsionuntil fast pupation at 20°C and 16L:8D and then transfemed to the experimental regimenspresented ( plotted from data presented by Hudson 1977b).

DECEMBER, 1987 BULL. SOC. VECIDR ECOL 573

observed during summer and midwinter (Fig. 3). This Females collected from shelters in Kern Countyabundance pattern was somewhat different from that by Washino et al. ( 1962) did not exhibit a reproductivepresented by Washino et al. ( 1962) for adults collected arrest during either summer or winter ( Fig. 6). The

from shelters where abundance was highest in May single female collected during August was gravid.

Fig. 4). Washino et al. ( 1962) collected larvae during Collectively, CO, trap and metabolic status dataevery month of the year except August and September, indicated that in California Cs. inornata most likelyhowever, male abundance at shelters did not increase undergoes ieyiuductive quiescence during summer andmarkedly until the vernal rise in abundance. Thus, the perhaps winter.

consistent midwinter decline in abundance observed To verify field observations, we studied thewhen populations were monitored by CO, or New response of Cs. inornata from Kern County toJersey light trap catches may have reflected the experimental temperature and photoperiod regimens

depressive effect of cold night time temperature on produced in a series of light boxes held in a warm

adult activity rather than the actual decrease in numbers insectary( 25°C) and a cold building( 16°C). Fach box

of adult mosquitoes present in the environment. was fitted with its own timer and 25 watt bulb light

Abundance patterns in the Coachella Valley were source. The progeny of females collected by CO, trapssimilar to those in the San Joaquin Valley except that during April were reared from eclosion to emergence atwarmer midwinter nightly temperatures did not five photoperiods and two temperatures( Fig. 7). Adults

markedly depress trap catches and an early vernal were held under the test regimens for two weeks post-

temperature rise resulted in an earlier decrease in New emergence, after which 10 to 15 females were dissected

Jersey light trap abundance ( Fig. 5). and the length of the primary and secondary follicles

350

300 Coastal Marsh

Sacramento Valley

250 x x Sierra Foothills

manza 200

150

a

Z 100 +

50

74x + No Samples jn{ \

O N D J• F M A M J J A S O N D J F M A M

1975 1976 1977

Figure 2. Relative abundance of host-seeking Culiseta inornata ( females/CO, trap night) at three ruralhabitats in central California, 1975- 1977 ( redrawn from Meyer et al. 1982a).


80

O

70

60

z 50

F-

40

a

t

30

20

10

0 0

0D. • • • • 0 - CI • • • • • • •

J F MAM J J A S O N D J F M AM J J A S O N D J F MA MJ JA SOND1983 1984 1985

Figure 3. Relative abundance of host-seeking Culiseta inornata ( females/CO2 trap night) at the KernNational Wildlife Refuge, San Joaquin Valley, California, 1983- 1985 ( unpublished data).

measured. Neither temperature nor photoperiod matured to the resting stage after the initialmarkedly anested follicular maturation, indicating that degeneration.reproductive diapause was not induced under either In Kern County, the first females collected duringmidwinter or midsummer photoperiod and temperature the fall of 1986 were either parous or gravidconditions. Mean primary/secondary follicular ratios ( unpublished data), indicating that some females take aranged 1. 64 to 1. 95 and did not vary significantly blood meal prior to aestivating and remain gravid untilthroughout. fall when they emerge and oviposit. These field data

Since the data of Hudson( 1977b) indicated that a were similar to the spring observations of Dow et al.transition in photoperiod during fourth instar was ( 1976) in Colorado and supported our laboratorynecessary to induce diapause, we repeated our experiments, which indicated a lack of reproductiveexperiment using field collected LA larvae which were diapause. Meyer et al. ( 1982a) have shown that Cs.reared in nature under 11 to 12 hours of light and then inornata females are facultatively autogenous and thatplaced in the same experimental regimens shown in the proportion of autogenous females increases duringFigure 7. The follicular ratio decreased significantly to winter as a function of decreasing temperature.less than 15 under conditions of 10 to 16L at 16°C. Therefore, some of the gravid females collected duringHowever, most ovarioles in these groups possessed spring, but not late summer, may have developed theirdegenerative dilatations indicating continued eggs autogenously without imbibing a blood meal.endocrine activity, which is not associated with a true Although females may not undergo areproductive diapause. Most likely the size of the reproductive diapause, they may undergo aprimary follicles were small because they had not yet physiological preparation for aestivation by depositing

DECEMBER, 1987 BULL SOC. VECDDR ECOL 575

400

300

8 p x x Males

oFemales

a

o200 o 0

is

34 V x/

X

Z 100 x

x

x

x

0

x\ ° x/

J F M A M J J A S 0 N D

Figure 4. Relative abundance of resting Culiseta inornata ( total males and females collected resting inshelters during each month), Kern County, California, 1952- 1961 ( plotted from data presentedby Washino et aL 1962).

2. 5

x x Males

z 2.0a

E--.Females

t)1. 5 p

r po

1. o oz

0.5

z

x/

x\ . 0x

0.0 _ x• gyp\

J F M A M J J A S O N D I P M A M J J A S O N D J

1975 1976

Figure 5. Relative abundance of phototactic Culiseta inornata ( log10[ y+ 1] adults/New Jersey light trapnight), Coachella Valley, California, 1975- 1976 ( redrawn from Barnard and Mulla 1978a).

576 BULL SOC VECIDR ECOL DECEMBER, 1987

Unfed Blood Fed Gravid

100— — — — — —

90

80—

70—

60 —

a 50—

40 —

11.

ire/r

10—

0Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Figure 6. Metabolic status of resting Culiseta inornata females collected at shelters in Kern County,California, 1952- 1961 ( redrawn from Washino et al. 1962).

2.0 —

1. 5 — V1. 0 --

0.5

0.0

Temp (° C) 25 16 25 16 25 16 25 16 25 16

Photoperiod 8L: 16D 1OL: 14D 12L: 12D 14L:10D 16L:8D

Figure 7. Mean primary/secondary follicular length ratios for Culiseta inornata females from KernCounty, California, which were reared from ecolsion to emergence and then held for 13- 15 dayspostemergence at the temperature - photoperiod regimens presented in the figure( unpublisheddata).


70-

60-

50-

340

30—

20-

10—

f. r

S O N D J F M A M J J A S O N D J FN= 5 33 214 48 81 56 29 19 12 4 0 0 4 47 183 61 43 29

1975 1976 1977

Figure 8. Lipid content(% by weight) of Culiseta inornata females collected by New Jersey light trapin the Coachella Valley, California, 1975- 1977 ( redrawn from Barnard and Mulla 1978b).

hypertrophic fat. Observations by Barnard and Mulla Host-seeking continues throughout the year and blood-1978b) in the Coachella Valley indicated a three-fold fed or gravid females can be collected during every

increase in the lipid content of females collected in New month. However, Culiseta inornata does respond toJersey light traps during March-June( Fig. 8). Females photoperiod cues during early summer and prepares fordisappeared during July and August and those collected aestivation by depositing hypertrophic fat. During lateat light traps in September and October had depleted July to early September, females essentially disappeartheir preaestival fat reserves. and have yet to be collected in large numbers in natural

Barnard and Mulla ( 1977) demonstrated in the or artificial shelters, CO2 or New Jersey light traps.laboratory that fat deposition was induced by Survival during the hot weather is dependent upon fatlengthening photophase independent of temperature reserves, which are accumulated regardless of

Fig. 9). Of considerable interest was the comparable reproductive status. Although induced by photoperiod,lipid deposition rates of blood-fed and nonblood-fed aestivation is rapidly terminated by changes infemales, which indicated that the mechanisms temperature and during midsummer in Kern Countyresponsible for fat deposition were independent of females can be collected host seeking at CO2 traps orfactors controlling reproductive activity. All blood-fed resting in shelters.females developed their eggs normally and did not The decrease in abundance during midwinter isexhibit gonotrophic dissociation similar to that des- more difficult to explain. Larvae, pupae, and newlycribed for some Culex and Anopheles. emerged adults can be collected at breeding sites

Thus, Cs. inornata from California do not enter throughout winter. However, cool evening temperatureeither a winter or summer reproductive diapause. during winter reduces host seeking and dispersalAestivation is accomplished by reproductively activity and few females can be collected in red boxes orquiescing females, which may be gravid or parous. host seeking. Adults can be collected from rodent


70 -

Blood-Fed Females Nonblood-Fed Females

60 —

50 -

40 -

30 -

10 —

o

Temp (° C) 15 20 25 15 20 25 15 20 25 15 20 25

Photoperiod 8L: 16D 16L:8D 8L: 16D 16L:8D

Figure 9. Lipid content(% by weight) of blood-fed and ruffed Culiseta inornata females which werereared from eclosion to emergence and held at the temperature - photoperiod regimens

presented in the figure for 21 days after emergence. Females were offered 10 percent sucrose

or a restrained chick on days 6- 15 ( redrawn from Barnard and Mulla 1977).

burrows on warm days. Apparently, there is no Barnard, D. R. and M. S. Mulla 1978a The ecologyphysiological preparation for this weakly maintained, of Culiseta inornata in the Colorado Desert of

transient winter quiescence, since Barnard and Mulla California: seasonal abundance, gonotrophic

1978b) found no winter change in the accumulation of status and oviparity of adult mosquitoes. Ann.

lipid reserves. Thus, winter dormancy in Cs. inornata Entomol. Soc. Am. 71: 397-400.must be classified as a cold weather quiescence.

AcknowledgementsBarnard, D. R. and M. S. Mulla. 1978b. Seasonal

variation of lipid content in the mosquito, Culiseta

I thank Drs. W. C. Reeves and R. P. Meyer, inornata. Ann. Entomol. Soc. Am. 71: 637-639.

University of California, Berkeley, and Dr. A. R. Barr,University of California, Los Angeles, for helpful Barr, A. R. 1957. A new species of Culiseta ( Diptera:

suggestions and comments during the preparation of Culicidae) from North America. Proc. Entomol.

this manuscript. Soc. Washington 59: 163- 167.

REFERENCES CITED Barr, A. R. 1985. Population regulation of immature

Culiseta incidens. Pgs. 147- 154. In: Ecology ofBarnard, D. R. and M. S. Mulla. 1977. Effects of

mosquitoes: proceedings of a workshop.photoperiod and temperature on blood feeding, Lounibos, L. P., J. R. Rey, and J. H. Frank Eds.).oogenesis and fat body development in the

Florida Medical Entomology Laboratory, Veromosquito, Culiseta inornata. J. Insect Physiol. 23:

Beach, Fl., 5791261- 1266. pp.


Bates, M. 1949. The natural history of mosquitoes. Meyer, R. P., R. K. Washino, and T. L. McKenzie.

New York, N.Y., 379 pp. 1982a. Studies on the biology of Culiseta inornataDiptera: Culicidae) in three regions of central

Buxton, J. A. and O. P. Breland. 1952. Some species of California, USA. J. Med. Entomol. 19: 558-568.

mosquitoes reared from dry materials. Mosq.News 12: 209-214. Meyer, R. P., R. K. Washino, and T. L. McKenzie.

1982b. Comparisons of factors affectingDarsie, R. F. and R. A. Ward. 1981. Mosquitoes of preimaginal production of Culiseta inornata

North America, north of Mexico. Mosq. Syst. Williston) ( Diptera: Culicidae) in two different

Suppl. 1: 1- 313. habitats in central California. Environ. Entomol.

11: 1233- 1241.

Dow, R. P., L. C. LaMotte, and G. T. Crane. 1967. Post-

hibernating Culex tarsalis and Culiseta inornata: Morris, C. D., R. H. Zimmerman, and L. A. Magnarelli.

oviparity and tests for the virus. Mosq. News 36: 1976. The bionomics of Culiseta melanura and

63- 68. Culiseta morsitans d)ari in central New York

Diptera: Culicidae). Ann. Entomol. Soc. Am. 69:

Frohne, W. C. 1953. Natural history of Culiseta 101- 105.

impatiens ( Wik.), (Diptera Culicidae) in Alaska.

Trans. Am. Microscop. Soc. 72: 103- 118. Siverly, R. E. 1967. The occurrence of Aedes

abserratus ( Felt and Young) and Culiseta

Frohne, W. C. 1954. Mosquito distribution in Alaska melanura ( Theobald) in Indiana Mosq. News 27:with especial reference to a new type of life cycle. 116.

Mosq. News 14: 10- 13.Wallis, R. C. 1953. Notes on the biology of Culiseta

Hopla, C. E. 1970. The natural history of the genus melanura ( Coquillett). Mosq. News 14: 33- 34.Culiseta in Alaska Proc. NJ. Extermin. Assoc.

57: 56-70. Wallis, R. C. 1962. Overwintering Culiseta melanuralarvae. Proc. Entomol. Soc. Wash. 64: 119- 122.

Hudson, J. E. 1977a. Seasonal biology of Anopheles,Culex and Culiseta in central Alberta (Diptera: Wallis, R. C. and L. Whitman. 1968. Oviposition ofCulicidae). Ph.D. Diss., University of Alberta,

Culiseta morsitans ( Theobald) and comments on384 pp'

the life cycle of the American form. Mosq. News

Hudson, J. E. 1977b. Induction of diapause in female28: 198-200.

mosquitoes, Culiseta inornata, by a decrease inday length. J. Insect PhysioL 23: 1377- 1382. Washino, R. K., R. L. Nelson, W. C. Reeves, R. P.

Scrivani, and C. H. Tempelis. 1962. Studies on

Joseph, S. R. and W. E. Bickley. 1969. Culiseta Culiseta inornata as a possible vector of

melanura ( Coquillett) on the eastern shore ofencephalitis viruses in California. Mosq. News

Maryland ( Diptera: Culicidae). Univ. Maryland 22: 268-274.

Ag. Exp. Sta. Bull. A-161: 1- 83.Wesenberg-Lund, C. 1921. Contribution to the biology

Mansingh, A. 1971. A physiological classification of of the Danish Culicidae. Mem. Acad. Roy. Sci.dormancies in insects. Can. Entomol. 103: 983- Ltrs. Copenhagen, 210 pp.1009.

Wilkins, O. P. and O. P. Breland. 1949. Recovery of theMarshall, J. F. 1938. The British Mosquitoes. London: mosquito Culiseta inornata from dry material.

Brit. Mus. ( Nat. Hist.), 341 pp. Proc. Entomol. Soc. Wash. 51: 27-28.

BULL SOC VECIOR ECOL, 12(2): 580-583 DECEMBER, 1987

FUTURE OPERATIONAL CONSIDERATIONS'

R. D. Sjogren2, D. J. Dobbert2, and S. Palchick2

Accepting an invitation to speak on the broad topic computer use in operational programs has occurredof future directions in vector control is a presumptuous with people who in the past 20 years have moved from

undertaking. The senior author speaks from a pencil and paper data management, through hand-heldbackground of 26 years experience in vector control calculators, now to computers. In most instances,programs in the United States. Academic training, people just entering the computer era have littletechnical literature, in-house research, the insights and appreciation of the critical role that planning and qualityexperience of co-workers, and a good measure of control play in data acquisition and analysis. Dataintuition have provided the basis for decision making. collection procedures should be shaped by the questionsDirecting control programs has depended to a great to be answered and the data necessary to adequatelyextent on" seat of the pants" intuition. Over the years, answer those questions.

the " seat of the pants" has broadened with experience. Statisticians and data analysts have long advised,However, it has not kept up with the current state of the " See me before you do the work, not after"; so it is withart in the field of information management the collection of data to be managed by computer.

Information management encompasses many Future problems can be avoided by first consulting withareas integral to vector control. These extend from an individual knowledgeable in data analysis and

specifying basic requirements of data management to research design, before you begin collecting data.utilizing this information for models of vector Unless the error rate of the data is known and reduced topopulation dynamics. Intertwined with all aspects of an a level acceptable for future decision making, the valueeffective program is reliable communication. Within and effort expended to collect the data will be lostthis framework, a quality control program can be used Collecting high quality, relatively error free,for independent assessment of data collected and work operational data by field staff while they are doing theperformed. With reliable data, we can further address work is a difficult task. Few operational programsconsiderations for the future from a philosophical and recognize the care and precision with which the dataoperational viewpoint must be collected. This problem is compounded by the

fact that field staff are expected to gather data whileData Management performing their necessary duties.

Mere intuition is insufficient to contend with the Good data management comes at a price.rapid advancement of personal computer technology, Pretending that computer utilization will enhancethe complexity of multifaceted control programs, program operations, without paying the price, willincreased focus on potential environmental impacts and relegate computer utilization to only an image of amonitoring requirements, and the importance of progressive operation. The importance of accuratelyaccurate data collection with which to direct large scale quantifying and tracking data input on each programfield operations. Intuition must be augmented by state activity cannot be overemphasized. It is the only wayof the art data management procedures capable of that future cost effectiveness analysis can be conductedproviding quantitative data on which to base cost-effective day-to-day program decisions. Communication and Quality Control

High quality data management practices will be It is impressive how accurately communication canrequired to take advantage of, and keep pace with, the convey the work needed and, with conscientiousadvances in vector control technology. Most program application, produce the results needed. However, it ismanagers recognize the benefits offered by the rapidly not realistic to assume that communications retain their

advancing field of computer science. Extended intended meaning as they pass from program directors


2Metropolitan Mosquito Control District, 2380 Wycliff St., St Paul, MN 55114, U.S.A.


and supervisory staff down to seasonal workers. It is quality assurance program.difficult to ascertain that they will be understood and Concomitant with operational concerns, theaccurately interpreted, even when committed to paper. accuracy and environmental impact of vector control

These gaps in communication often are not readily programs has come under increased public scrutiny inperceived. Foremen and supervisors are responsible for recent years. We have recently been directed to preparethings going correctly in areas of their jurisdiction, our second Environmental Impact Statementhence they are often reluctant to discuss the work concerning our control program. Vector controlquality of their field staff. Unless specifically districts should not be surprised if they too are facedaddressed, problems often do not surface for resolution, with this responsibility. Availability of a reliable databut rather compound over time through lack of feedback base can facilitate this task.communication.

One solution for this lack of feedback from field Vector Management Modelstaff is to open and maintain channels of Systems modeling has been used for some time bycommunication and accountability between field defense contractors for weapon systems development,operations staff and program administration. Mother NASA for the space program, management for businesssolution is to conduct a concunent quality assessment operations, natural science researchers to gain anprogram to confirm that field personnel perform in the understanding of biological, physical, and chemicalmanner that the program director anticipates. Secondly, processes, and by entomologists for insect populationthe quality assurance program can confirm that field modeling. The application of modeling in vectorpersonnel understand and implement the directives of control will increase as the understanding of how simplethe managers as intended. Qkility assurance is a mature modeling principles can be used becomes morescience of its own in the manufacturing field. Quality available and widely understood.control professionals can offer much to ongoing vector The value of modeling depends upon the intendedcontrol programs. uses for the model and the user. Graphic models

Most field operational staff began working with illustrate components and relationships of processes orvector control programs in early adulthood after high systems. Computer simulation models allow programschool or during the summer months of college. Due to leaders to look into relationships which may have atheir love of the outdoors and interest in the work, these significant impact on the end resultpeople often stay to make a career out of working in the The primary value of modeling is the opportunity tofield. Over the years such staff develop extensive examine how the system behaves without the cost ofexperience and intuition on what to expect when actual implementation. While identifying thechanging conditions are encountered. As programs components and their relationships, the model builderincrease in size, a larger percentage of the work force is gains insight into the process being modeled. Questionscomposed of seasonal employees working under the are raised and their answers lead to further questions anddirection of older staff who have come up through the clarification. Unclear areas are identified.ranks. Operational programs depend on the transfer of How accurately the model visualizes the real lifeknowledge and experience from the older staff to the situation determines the quality of the model. Whetherseasonal employees. the model provides insights into questions it was

The nature of vector control operations requires designed to address determines its usefulness. Thework to be performed at many geographic areas at the model is never true, false, complete, or incomplete; it issame time. It is physically difficult to verify that the only in a state of usefulness. This means a model mustfield work performed by each employee meets be updated regularly as the questions it must addressacceptable standards of implementation. Advanced change, the real life situation it depicts changes, orprograms require control materials to be used at more further insight into the situation it depicts becomesminute levels with accurate timing and delivery. The available.

opportunity for failure to communicate in sufficientdetail increases and the consequences of errors Future Considerationscompound. While consolidation is seldom a popular topic, it is

It is difficult to know what is being done under field difficult to argue against the regional control concept inconditions over large geographic areas without an which a unified program operates under one

independent assessment of the implementation of administrative canopy. Insect populations, especiallycontrol procedures. This information is collected for the migratory populations, do not recognize politicalMetropolitan Mosquito Control District through a boundaries. M effective vector control program must


go where the insects are and not be restricted by artificial projects are conducted in prominent residential areas

constraints. A properly designed regional program can and if reports comparing mosquito biting levels insideprovide increased technical support where and outside the demonstration area are distributed

specialization is needed in vector control programs. A monthly. When information on the environmental

unified program with coordinated control activities is safety of the program accompanies programimportant when the insect vector is capable of long effectiveness, the two most frequently asked questionsrange flight which transcends political boundaries. am answered.

Under such circumstances, the assignment of resources A trend will probably develop towards morecan best be done by a single purposed agency. specialized training of field staff. This specialization

Greater emphasis needs to be placed on identifying will provide increased efficiency and quality, and willthe goals of vector control programs. It is common to simplify the day- to-day decision process in programform vector control programs during periods of high operations. In Minnesota, such specialization has been

disease or vector annoyance levels to " do something successful in Coquillettidia perturbans control,

about the problem." It is less common to establish goals Similium control, LaCrosse Encephalitis vector control

for measuring a program' s effectiveness prior to activities, and quality assurance measures. In each

implementation of a program. instance, staff responsibilities are regional and remain

Only when such goals are identified and clearly within the specialized nature of the work.

understood by the policy-making body, agency staff, Conventional Aeries control programs largelyand local citizens can everyone understand where the await a flooding, which initiates a brood, and in theprogram is going, when it will get them, and what it will succeeding days work feverishly to reach as manycost. Too often programs begin vaguely and continue breeding grounds as possible to hold the populations inover the long term with vague, undefined objectives, check to the greatest extent possible with available

and without public support due to lack of resources. This approach is a poor use of manpower and

communication. resources and rarely is capable of achieving control overAs in any business, vector control programs must a sufficiently large geographical area to counteract the

be marketed to their customers ( i.e. citizens) to inform infiltration of adult mosquitoes from uncontrolled

them of the benefits of the services being provided adjacent areas. Such efforts largely relegate the controlEffective vector control programs provide services activities to a " firehouse approach." When you' re

desired by the general public at a low cost and possibly needed, you' re needed; and when you' re not, you await

lower environmental impact than that afforded by the next flooding.individual homeowner pesticide applications. When Where vector control operations focus on

citizens recognize the benefits received, their synchronous broods of Aedes mosquitoes, control

willingness to pay for the service can be up to five times measures will shift increasingly to a preventive rathergreater than the service costs to deliver. Willingness- to- than a reactive program. These operations may requirepay surveys, based on denied time values for favored substantial resources to control all the significant

out-of-door activities, help governing boards to breeding grounds within the flight range of the speciesaccurately perceive the level of service desired by and within the mosquito developmental period

taxpayers. Preventive control measures, which employWhere significant vector disease transmission or prehatch and long term controlled release formulations

annoyance problems are present, demonstration of environmentally compatible control materials,

projects conducted in worse case areas can demonstrate allow each employee to treat up to eight times more areato a decision-making body that effective control can be than with previous methods. Altosid controlled release

achieved. In the process of doing so, the cost per unit briquets and Altosid controlled release sand granules

area can also be determined. It is unrealistic to expect afford significant operational benefits through

that elected officials or administrators will support advanced applications to highly productive breedingexpansion of programs, based on the word of program grounds, thus, making better use of aircraft and groundstaff, without being convinced of the program crews. To offset the pressure of controlled release

effectiveness and knowing what the ultimate cost will formulations on resistance development, 20 and 40 daybe to achieve the program goals. Where program controlled release Bti formulations are under

expansion is needed, demonstration programs running development to mitigate resistance development byone to two years can be effectively used to demonstrate alternating selection pressure.program benefits. The program effectiveness can be The focus on environmental aesthetics will

readily understood by citizens if such demonstration continue to increase and draw vector control programs

DECEMBER, 1987 BULL SOC VECPOR ECM 583

into center stage for public review. Active public identified.

information programs to educate citizens about As programs increase in complexity and/or size,environmental factors associated with vector control accountability and attention on cost effective programprograms should be considered as important as the operations increase accordingly. When programs

control activities themselves. Judicious selection of develop beyond where program managers can track allcontrol materials based on effectiveness, nontarget the pieces, well organized and accurate data sets are

impact, and finally cost, gain public support for necessary to maintain an understanding of fieldoperation programs. conditions and relationships upon which to base

As the complexity of operational programs program decisions. The cost to obtain an accurate dataincreases with the number of employees and different set must be weighed against the cost incurred fromtasks performed, it becomes more difficult to deter- making a wrong decision with inadequate information.mine the real costs of each control activity and Such data needs are not unique to vector controlassociated options. Unless each program component is programs. We have all heard how rapidly informationcosted out accurately, program administrators must management systems are developing in the businessaccept the responsibility for guessing which alter- world. Expert systems and artificial intelligence arenative is best, or at best making decisions with being applied to decision making and service systems ininadequate data. In addition to laboratory effective- manufacturing, medicine, mental health, education andness, we need to determine the cost effectiveness of each training, and psychology. The vector control fieldcontrol procedure in the field. The environmental should evaluate its direction and consider the

impact and unintended outcomes also need to be application of those technologies into its operations.


MANPOWER NEEDS IN DISEASE ENDEMIC COUNTRIES1

R. Slooff 2

This paper specifically addresses the manpower of WHO. Within this collaborative activity, a workshopneeds of disease endemic countries in respect of vector was held in Panama in 1985, on the Manpower and

biology and control specialists for the guidance of Training Needs in the American Region. This

disease control operations and for carrying out the workshop was preceded by in-depth studies in Panama,necessary applied research. This restriction does not Ecuador, Guatemala, and Colombia, resulting inimply that the manpower issues in other disciplines or at country profiles, which were used as working papers

other levels should be considered less important and as a basis for the workshop deliberations. A similarAs the speciality of vector biology and control, workshop is being planned for the southeast Asian

usually referred to as medical entomology, is concerned Region. It may be held in Thailand in either late 1987with all human diseases and zoonoses carried by or early 1988, and it will focus on in-depth countryvectors, the discipline covers a very wide range of studies to be performed in Thailand, India, Burma, and

vector species, transmission cycles, and control Indonesia.

options. In disease control programmes, the duties of Such studies and others already completed show anmedical entomologists include vector incrimination, alarming situation in many disease endemic countriesvector bionomics, epidemiology, choice of control inasmuch as major disease control programmes either

strategy, supervision or evaluation of control are being directed on the basis of vastly insufficientimplementation, and the monitoring of its impact The vector control expertise or are not even beingmedical entomologist engaged in applied research faces considered for lack of information on vector species,

a multitude of urgent research questions in the field of their biology, and means of control applicable underpesticide development, the use of biological control conditions prevailing in the country.agents and environmental control, the development of The major constraints for remedying the situationself-protection methods, and other approaches for are ( 1) lack of training facilities, both in the diseaseprimary health care, in addition to the wide and largely endemic countries and in potential donor countries, ( 2)

unexplored field of transmission manipulation by lack of training components in externally financedimmunological means or genetic engineering. These projects, ( 3) lack of attractive career prospects in

tasks are challenging and the work can be very disease control or applied research programmes, and( 4)

rewarding professionally. In general, the medical " brain drain" to the commercial sector, universities or

entomologist of today is graced with more problems of research laboratories, and to industrialized countries.

greater complexity than his colleagues of a generation WHO and TDR are involved in several activities

ago. aimed at the improvement of this situation. The

As the title of this paper suggests, the disease collaboration between WHO and the Fogartyendemic countries have manpower needs in medical International Center and US AID was alreadyentomology that are inadequately met in many mentioned. More efforts will be needed in analyzinginstances. Just how great the unsatisfied demand is, manpower situations and in encouraging remedies to behowever, remains largely unknown. One attempt to taken by appropriate institutions worldwide. Through

clarify the situation and to provide manpower planners its research capability strengthening and institutionand training institutions with data for more concrete strengthening endeavors, TDR is already contributingguidance is being executed by means of collaboration to improvements, particularly in developing countries.between the Fogarty International Center, WHO, and At present, several M.Sc. courses in tropical countries

USAID. This project aims at the analysis of manpower receive TDR and/or WHO support ( e.g., in Panama,and training needs in important disease endemic regions Cote d' Ivoire, Nigeria, Kenya, India, Thailand, and

Presented at the SOVE Symposium, AMCA Annual Meeting, Seattle, Washington, 31 March 1987.

2Director, Division of Vector Biology and Control, World Health Organization, 1211 Geneva 27, SWITZERLAND.


Indonesia), with varying degrees of success. More recognized specialization at the M.Sc. level and atefforts are needed to evaluate the effects of the postgraduate levels.

assistance provided and to improve the adjustment of In reviewing the situation, the most acute needs are:some of these training courses to meet the needs of ( 1) in- country situational analyses to clarify thedisease vector control programmes and the applied manpower and training needs worldwide, ( 2) theresearch that is necessary to support these. establishment of regional M.Sc. training programmes in

National institutions, both in industrialized and disease endemic countries, ( 3) achieving improveddeveloping countries, are already playing a significant international compatibility in specifications for androle in bridging the gap between supply and demand in standards of M.Sc. qualifications, and ( 4) improve-the field of medical entomology, but substantially more meats in career prospects for medical entomologists,input is required Particularly needed are: ( 1) more particularly in disease control programmes.compatibility between the academic research discipline Medical entomologists should be more multi-and the operational needs of disease vector control, ( 2) functional within a wide range of vector and pest control

training components in vector control and research and have a profound understanding of epidemiology, inprogrammes carried out in disease endemic countries, order to be able to adapt to the needs of different posts

3) raising disease vector biology to the status of a and the problems raised by changing disease priorities.

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INVITATION TO CONTRIBUTING AUTHORS

The Bulletin publishes results of new, original re- Bull. Soc. Vector Ecol., 9( 1): 30- 36; Reisen, 1984, Bull.search, or the review thereof, and invited and submitted Soc. Vector Ecol., 9( 1): 6- 16). An ABSTRACT is re-

presentations from national or local SOVE proceedings quired for review presentations; when and where ap-

in the field of vector biology and control and related propriate, a REFERENCES CITED section and textual

disciplines. Submitted manuscripts are acceptable in headings and subheadings are recommended; an Ac-English, French, Spanish, Italian, or German. Foreign knowledgements section is optional. The Invitational

language manuscripts must include an English summary, and Submitted Presentations manuscripts are reviewed

An original manuscript typed and double- spaced, plus and edited for style, typographical errors, and syntax.

two complete copies must be submitted. The copies will There are no page charges for Invitational Presentationsbe sent to at least two outside reviewers. It is assumed published in the Bulletin; page charges are $ 25 per

that the contributions are based on original research that printed page for Submitted Presentations.

has not been submitted for publication or publishedelsewhere. Manuscripts are edited with reference to the Submitted Papers:

current style of the Bulletin( allowing for changes found These articles are contributions from vector biolo-in this revision of the Instructions), which generally gists at large that are sent to the Bulletin for publicationfollows the Council of Biology Editors ( CBE) Style and represent original research( see Mulla and Darwazeh,Manual 1979, 4th Edition. AIBS, Washington, D. C. 1984, Bull. Soc. Vector Ecol., 9( 1): 51- 58), or synthesisEdited manuscripts ( with reviewers' comments when articles that thoroughly cover some aspect of vectorappropriate), pre- galley proof drafts, and galley proofs biology ( see Balashov, 1972, Misc. Publ. Entomol. Soc.are returned to the corresponding author in order to Am., 8( 5): 160- 376; Rvckman et al., 1981, Bull. Soc.resolve any editorial questions before final printing. Vector Ecol., 6: 1- 92). Research Notes represent original

research and are no more than two printed pages inTypes of Articles length( see Bennett, 1983, Bull. Soc. Vector Ecol., 8( 2):Proceedings: 139- 140). Submitted Papers are evaluated by the ref-

Proceeding' s articles consist of Invitational and Sub- erees for originality, pertinence, and presentation of the

mitted Presentations( c. f.,Submitted Papers) from SOVE subject material in addition to style and form. Page

Regional and National Conferences and may be historicalcharges are $ 25 per printed page. See the INSTRUC-

reviews( see Gerber 1984, Bull. Soc. Vector Ecol., 9( 1): TIONS TO CONTRIBUTING AUTHORS section in the

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or specific research articles ( see Mitchell et al., 1984, more information.

Send manuscripts to:

Bulletin of the Society of Vector EcologistsDr. James P. Webb, Jr., Editor

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