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Recruitment behavior in stingless bees, Meliponascutellaris and M. quadrifasciata. I. Foraging at food

sources differing in direction and distanceStefan Jarau, Michael Hrncir, Ronaldo Zucchi, Friedrich Barth

To cite this version:Stefan Jarau, Michael Hrncir, Ronaldo Zucchi, Friedrich Barth. Recruitment behavior in stinglessbees, Melipona scutellaris and M. quadrifasciata. I. Foraging at food sources differing in directionand distance. Apidologie, Springer Verlag, 2000, 31 (1), pp.81-91. <10.1051/apido:2000108>. <hal-00891699>

Original article

Recruitment behavior in stingless bees, Meliponascutellarisand M. quadrifasciata. I. Foraging at food sources differing

in direction and distance

Stefan JARAUa, Michael HRNCIRa, Ronaldo ZUCCHIb,Friedrich G. BARTHa*

a Universität Wien, Biozentrum, Institut für Zoologie,Abteilung Physiologie – Neurobiologie, Althanstraβe 14, A-1090 Wien, Austria

b Universidade de São Paulo, Faculdade de Filosofia e Letras,Departamento de Biologia 14040-901 Ribeirão Preto, SP, Brazil

(Received 28 April 1999; revised 6 September 1999; accepted 22 September 1999)

Abstract – The two stingless bee speciesMelipona scutellarisand M. quadrifasciata recruit nestmatesto a rich foraging site. We tested this with feeders up to 140 m away from the hive. Foragers ofM. scutellaris communicated direction (up to 140 m) more accurately than distance (up to 30 m)whereas those of M. quadrifasciatacommunicated direction only up to 30 m and distance up to40 m. Our data indicate that in both species recruitment is divided into two temporal phases. Whereasin an initial phase alarmed nestmates search for food at random, bees leaving the hive in the fol-lowing phase are obviously provided with information about its specific location. As a consequenceafter 35 minutes (M. scutellaris) and 85 minutes (M. quadrifasciata), respectively, significantlymore newcomers arrive at the feeder than at an identical control feeder. The differences found in therecruitment success of M. scutellarisand M. quadrifasciataare discussed in regard to the differentdemands of their natural habitats.

stingless bee / foraging / recruitment / direction and distance communication / Meliponaspecies

Apidologie 31 (2000) 81–91 81© INRA/DIB/AGIB/EDP Sciences

* Correspondence and reprintsE-mail: friedrich.g.barth@univie.ac.at

S. Jarau et al.82

1. INTRODUCTION

Stingless bees (Meliponinae), like hon-eybees (Apinae), are eusocial insects. Com-munication between individuals is impera-tive for the survival of their colonies and inmany species the recruitment of field beesby foragers seems to be as important for theexploitation of rich food sources as it is inhoneybees [11].

In Melipona scutellaris, one of thespecies studied by us, foragers failed to com-municate the distance of a food source inthe experiments reported by Lindauer andKerr [11]. In addition the number of new-comers at the feeder was only slightly largerthan at a control feeder in an experimentdesigned to test the ability to communicatedirection [11]. Later, Nieh and Roubik [14]found these results not to be statistically sig-nificant. It thus remains uncertain whetherforagers of M. scutellarisare indeed com-municating information on the distance anddirection of a food source. Similarly, forM. quadrifasciata, the other species exam-ined in the present study, it only seems tobe clear that direction is communicated moreaccurately than distance [9]. The signifi-cance of acoustic signaling for distance com-munication is still doubtful and its functionremains uncertain [2, 3, 5, 14]. The avail-able studies do show, however, that suc-cessful foragers of both M. scutellarisandM. quadrifasciatacause some nestmates toleave their nest in search of food. Unfortu-nately, there have been hardly any attemptsto further clarify the recruitment behaviorof these two species in detail for the last 35to 40 years [7] nor is recruitment behaviorfully understood in any other stingless bee.

Nieh and Roubik [14] and Nieh [13],treating their data statistically, recentlydemonstrated that foragers of Meliponapanamica recruit nestmates to a food sourcein a specific direction, distance, and evenheight above ground without using scentmarks over long distances.

The present study on M. scutellarisandM. quadrifasciataseeks to answer the fol-

lowing questions: (1) Do foragers recruitnestmates to food sources in specific direc-tions and at specific distances from the hive?(2) How efficient is their recruitment? (3)Does recruitment success follow any tem-poral pattern?

2. MATERIALS AND METHODS

2.1. Study site and colonies

The experiments were carried out on theRibeirão Preto Campus of the Universidadede São Paulo, Brazil between September1996 and February 1997. We used onecolony of Melipona scutellarisand onecolony of M. quadrifasciata. The naturalhabitat of both species are the regions of theformer atlantic rainforest (Mata Atlântica),with M. scutellarisoccurring in NortheastBrazil (from Pernambuco to the South ofBahia) and M. quadrifasciataoccurring inthe southeast (from Minas Gerais to SantaCatarina) (João M. F. de Camargo, unpub-lished data). Both species nest in tree cavi-ties with 400–600 and 300–400 adult indi-viduals, respectively [11]. Worker size is10–12 mm in M. scutellarisand 8–10 mm inM. quadrifasciata. Our experimental colonieswere kept in wooden boxes inside the labo-ratory with plastic entrance tubes (15 mmin diameter) inserted through the wall of thebuilding.

2.2. Feeding stations

As feeders we used Schott-Duran labo-ratory glass dishes (27 mm high, 40 mm indiameter) placed upside down on hexago-nal plexiglass plates (77 mm in diameter)with six radially arranged grooves allowingthe bees to take up the sugar water. Thefeeders were filled with sugar water(0.75 mol.l–1 for training, 1.5 mol.l–1 forexperiments) scented with 3 µl essence ofrosewood (Aniba rosaeodora)/ml solutionand rested on stools 90 cm above ground.

Recruitment behavior in stingless bees. I

consecutive days. Figure 1 shows all feederlocations used in the experiments.

The time of every arrival of the five for-agers at the feeder was recorded as werenumber and arrival time of the newcomers atboth, feeder and control feeder. All new-comers were caught at the feeders, kept inglass vessels, and provided with sugar wateruntil the end of the experiment.

To test the efficiency of recruitment andwhether its success changed during the for-ager’s phase of activity, the data of all train-ing experiments were pooled. An experi-ment’s entire duration (180 minutes) wasdivided into sections of five minutes. Thenumbers of newcomers arriving at the feederor the control feeder, respectively, weresummed for each of these 36 intervals toidentify a possible temporal recruitment pat-tern. Since the experiments were carried outin the same area, at the same time of day(13 h to 16 h), at similar weather conditions,and using the same bee colonies, errors bypooling data based on different experimen-tal conditions were excluded.

2.3. Marking of bees

On the day before an experiment wemarked all bees landing on a feeder right infront of the colony entrance with a uniquecombination of two out of five different col-ors [4]. Unmarked bees showing up at afeeder during the experiments were cap-tured and marked at the end of the experi-ment (see training experiments).

2.4. Training experiments

A feeder containing a 0.75 mol.l–1 sugarsolution was placed in front of the hive.With five marked bees collecting regularlyat the feeder the food source was moved insteps of a few meters up to its final posi-tion. There the foragers were allowed to col-lect sugar water for another 15 minutesbefore the feeder was removed. Bees otherthan the trained foragers at the feeder werecaught and kept in a jar until the end of theexperiment.

Foragers were always trained between9 h and 11 h in the morning. After a breakwith no feeder each experiment began at13 h and lasted until 16 h. Early afternoonwas chosen for the experiments, because inother species of the genus Meliponanectarintake is known to be highest late in themorning and early in the afternoon [1, 17],suggesting that the propensity to be recruitedis particularly high at these times.

The experimental feeder offering a1.5 mol.l–1 sugar solution was installed atthe location the five foragers had beentrained to in the morning of the same day.5ml of the same solution were injected intothe entrance tube of the colony’s hive.Within a few minutes all five foragersshowed up at the feeder. A control feederwas installed at a location which differedfrom that of the experimental feeder onlyin either direction to the hive or distancefrom the hive. The feeders were never posi-tioned in the same direction from the hive on

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Figure 1. The locations of the experimentalfeeder relative to the bee colonies (indicated bythe nest symbol). The control feeders are notshown. North is indicated by the arrow, the num-bersrepresent distances (m) from the hive. sandq, feeding stations in experiments with Meliponascutellarisand Melipona quadrifasciata, respec-tively.

S. Jarau et al.

2.5. Statistics

For each training experiment and for thechanges in the recruitment success we cal-culated the χ2– probability (significancelevel p ≤ 0.05) of the observed distributionof newcomers at the feeder and at the controlfeeder.

3. RESULTS

3.1. Production of sounds dependingon sugar concentration

When using a 0.75 mol.l–1 sugar solu-tion during the training procedure foragersdid not produce any signals inside the hive

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Figure 2. Communication of direction in (a) M. scutellarisand (b) M. quadrifasciata. Black bars,the five foragers of each experiment; white bars, newcomers at the experimental feeder; shadedbars, newcomers at the control feeder; numbers beside bars, bees captured at each feeder. For eachexperiment the date, the compass directions of the feeding stations relative to the hive (E, N, NW, W,S, SE) and the probability for randomness of the observed distribution of newcomers at the feeder andthe control feeder, respectively, are given. The asteriskindicates that significantly more newcomersarrived at the control feeder than at the experimental feeder.

Recruitment behavior in stingless bees. I

In M. quadrifasciata(Fig. 2b) only atfeeder distances within 30 m from the hive,with one exception, significantly more new-comers arrived at the feeder than at the con-trol feeder. At a distance of 140 m, in oneexperiment significantly more newcomersarrived at the feeder but in the other exper-iment significantly more newcomers reachedthe control feeder. In the latter experimentthe control feeder was close to (4 to 7 m)two flowering trees. Some bees captured atour feeder carried pollen most likely col-lected on these trees.

3.3. Recruitment to a food sourcein a specific distancefrom the hive

In M. scutellaris(Fig. 3a), significantlymore newcomers reached the feeder thanthe control feeder when it was placed at adistance of 30 m from the hive, no matterwhether the control feeder was closer to the

nor were any newcomers recruited. Soundproduction, vibrations, and recruitment byforagers only occurred when we offered1.5 mol.l–1 sugar solution during the exper-iment.

3.2. Recruitment to a food sourcein a specific direction from the hive

In seven out of nine experiments withMelipona scutellaris, significantly morenewcomers arrived at the feeder than at thecontrol feeder which was located at the samedistance from the hive but in the oppositedirection (Fig. 2a). The success of therecruitment did not depend on the foodsource’s compass direction relative to thehive nor on its distance (30, 50, 70, 140 m)from the hive. However, the two experi-ments with the feeder at 70 m east and at70 m west, respectively, showed no signif-icant difference between the number of new-comers at the feeder and the control feeder.

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Figure 3. Communication of distance in (a) M. scutellarisand (b) M. quadrifasciata. For furtherdetails see Figure 2.

S. Jarau et al.

hive or further away. With the feeder at 50 mand 70 m, respectively, we only observedmore newcomers at the feeding station whenit was closer to the hive than the controlfeeder.

In M. quadrifasciata(Fig. 3b), signifi-cantly more newcomers arrived at the feederonly when it was placed 40 m away fromthe hive. In all other cases statistically equalnumbers of newcomers were captured atboth, the feeder and the control feeder. Inone experiment with the feeder at a distanceof 50 m from the hive significantly morenewcomers reached the control feeder,which was placed only five meters awayfrom the hive.

3.4. Recruitment efficiencyand temporal recruitment pattern

In Melipona scutellaris(Fig. 4a), thenumbers of newcomers at the feeder and atthe control feeder, respectively, were sta-tistically equal during the first 35 minutes ofthe experiments. After that initial phase sig-nificantly more newcomers reached thefeeder than the control feeder until the 105thminute, with only one exception betweenminutes 56 and 60. After 105 minutes thenumber of bees arriving at both the feederand the control feeder in general decreased.At this time the limited number of field beesin the colony probably had already beenremoved at the feeders to a substantialdegree. In M. quadrifasciata(Fig. 4b) sig-nificantly more newcomers arrived at thefeeder only between minutes 85 and 95 andbetween minutes 100 and 110. During thefirst 50 minutes of the experiments manybees left the hive, reaching the feeder andthe control feeder in almost equal numbers.In M. quadrifasciata, the number of beescaptured later than that in general decreasedwith time.

4. DISCUSSION

According to the few studies available,the success of recruiting nestmates and theability to direct them to the food differs con-siderably between species of stingless bees.Thus, while foragers of Trigona iridipen-nis are able to inform their nestmates aboutthe existence of a food source, they do notprovide them with any information aboutits location [10]. Melipona scutellaris,M. quadrifasciata, Trigona droryanaandNannotrigonasp. seem to represent an inter-mediate group regarding recruitment suc-cess, with only a few newcomers reachingthe food source [11]. Trained foragers ofT. silvestrisand T. jaty hardly recruit anynew bee whereas the recruitment success ofT. ruficrus, Scaptotrigonasp., Geotrigonasp. and Cephalotrigonasp. is similar to that

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Figure 4. Temporal recruitment pattern in (a)M. scutellarisand (b) M. quadrifasciata. Thenumbers of all bees recorded during the trainingexperiments were summed and blocked for peri-ods of five minutes. Solid line, newcomers at thefeeder;dashed line, newcomers at the controlfeeder. In the shaded sections significantly morenewcomers reached the feeder than the controlfeeder.

Recruitment behavior in stingless bees. I

seem to search for the food source at ran-dom, as they reached the feeder and controlfeeder in statistically equal numbers. It took35 minutes until significantly more new-comers arrived at the feeder than at the con-trol feeder, suggesting that the bees werethen provided with information about thefood’s location.

According to the present study therecruitment to a specific food location isless accurate in M. quadrifasciatathan inM. scutellarisalthough in this species therecruitment to a specific direction is quiteeffective up to distances ≤ 30 m. Again, likein M. scutellaris, the communication of dis-tance is not accurate. From the recruitmentpattern we concluded that, in M. quadrifas-ciata, recruited bees do not search for a foodsource at random, but that there is only poorcommunication about the location of a feed-ing site. Only during a short period in ourexperiments significantly more newcomersreached the feeder than the control feeder.

4.2. Comparison withMeliponapanamica

Both species of Meliponaexamined inthis study seem to recruit new bees to a foodsource less precisely than is reported forMelipona panamica [14] if only the signif-icance of the difference of the number ofnewcomers arriving at the feeder and thecontrol feeder, respectively, is evaluated.However, this may be due to different exper-imental procedures. Whereas we trained fiveforagers to a food source Nieh and Roubik[14] trained ten or fifteen foragers. Also,our experiments followed a strict time sched-ule and lasted for three hours each whereasNieh and Roubik [14] ended an experimentwhenever significantly more bees (p ≤ 0.05)had arrived at the experimental than at thecontrol feeder. Data on the duration of theirexperiments are not given, but some of themlasted for several days. When comparingthe absolute numbers of newcomers arrivingat the feeder, M. scutellaris(3–46) and

of the honeybee, Apis mellifera. Unfortu-nately, for the majority of these species theresults so far available are based on onlyone experiment and thus of only limited sig-nificance.

4.1. Direction versus distancecommunication

Our study confirms the now classicalobservations by Lindauer and Kerr [11] andby Kerr et al. [9] by providing evidence that(i) foragers of Melipona scutellarisandM. quadrifasciataindeed do recruit nest-mates to a rich foraging site and that (ii) inboth species communication of direction ismore accurate than communication of dis-tance.

According to our data, M. scutellarisfor-agers inform their nestmates adequatelyabout the direction to the food sourcewhereas the information on distance – if any– must be very poor. Recruited bees seem toleave the hive in the direction communi-cated by the forager and to search for a foodsource smelling like the sample previouslytaken in the hive. In other species of sting-less bees such as Trigona silvestris, T. flav-icornisand T. testaceicornisthe odor of thefood is indeed the most important factor incommunication [6]. Possibly the bees firstsearch at approximately 30 m from the hivewhich would explain why significantly morenewcomers were captured at the feeder thanat a control feeder at this distance. With thefeeder more than 30 m away, the beessearching for food first encountered the con-trol feeder with the same smell and food.Correspondingly, significantly fewer beesreached the control feeder when it was fur-ther away than the feeder. Future experi-ments will have to be carried out withunscented food to better understand the roleplayed by the food odor.

M. scutellarisleft the hive at a very earlystage of the experiment, obviously alarmedby a forager’s sound signals produced insidethe nest [5]. In this initial phase the bees

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M. quadrifasciata(4–37) turn out to recruit– or at least to alarm – their nest mates moreeffectively than M. panamica(5–14). Inaddition the colonies of M. panamicacon-tained more adult individuals (500-800) thanthose of M. scutellaris(400–600) andM. quadrifasciata(300–400).

According to Nieh and Roubik [14]M. panamicais even able to communicatethe height of a food source above groundlevel without using a scent trail. Unfortu-nately, no similar experiments are availablefor M. scutellarisand M. quadrifasciata.Like in M. panamicascentmarking andguiding flights are unimportant in the com-munication system of the other twoMelipona species, at least under certain con-ditions [5] and in disagreement with earlierobservations [7].

4.3. An ethoecological speculation

The differences we found betweenM. scutellarisand M. quadrifasciatamayreflect differences in their natural habitats.The regions of the Brazilian Atlantic rain-forest where M. quadrifasciatanaturallyoccurs are covered with dense vegetation,whereas M. scutellarislives in areas withopen forest (João M.F. de Camargo, unpub-lished data). Mass-flowering trees are themost important food plants of the highlyeusocial bees in the tropics [18, 19]. Thesetrees may be more abundant and easier toencounter in a dense forest (habitat ofM. quadrifasciata) than in an open forest(habitat of M. scutellaris). Thus a more orless random search may be an adequate strat-egy for M. quadrifasciata. In addition thebiomass of a colony is said to correlate pos-itively with the absolute foraging distanceand the effectiveness of communication[12]. The larger the colony or the greaterthe flight range, the greater the need for aneffective communication. The species inves-tigated here live in colonies of 300–400 and400–600 adult individuals, respectively.

Information on the flight range of sting-less bees is very scarce [15]. Roubik andAluja [16] determined maximum flightranges, which need not be equivalent to max-imum foraging ranges, for Trigona capitata(1.5 km) and Melipona fasciata(2.1 km) byreleasing marked bees at various distancesfrom the hive and recording those who foundtheir way home. For M. scutellarisno suchdata is available whereas 2.0 km is givenfor M. quadrifasciatain the literature [8].

4.4. Temporal pattern

In both species the temporal recruitmentpattern shows an initial phase where beesleave the hive and search for food sources atrandom before they obviously make use ofinformation about the location of a particu-lar food site. This finding suggests the fol-lowing sequence of events: (i) when a for-ager discovers a rich food source, she firstcommunicates its existence, smell, and qual-ity inside the hive. (ii) Alarmed nestmatesfly out looking for an equal food source atrandom. This may be a successful strategy inhabitats with mass-flowering plants, as itoccurs in tropical forests. (iii) Those beesthat have not found a food source by ran-dom search after a certain period of timethen leave the hive with information aboutthe location of a food site, or at least aboutits direction from the hive.

ACKNOWLEDGEMENTS

We are very grateful to Warwick E. Kerr,who kindly provided a colony of Meliponascutellarisfrom his private meliponary in Uber-lândia – Minas Gerais and shared his long expe-rience with stingless bees with us. We also thankSidney Mateus for his unfailing help in handlingthe bees. This work was partly supported by agrant from the BMFWK of Austria to SJ andMH and by money made available to FGB bythe Convenio between the University of SãoPaulo and the University of Vienna.

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Recruitment behavior in stingless bees. I

elle communique d’abord son existence, sonodeur et sa qualité à l’intérieur de la ruche ;2) les congénères alertées sortent et cher-chent au hasard une source de nourritureéquivalente. Ceci peut constituer une stra-tégie fructueuse dans des habitats, tels que laforêt tropicale, où les plantes fleurissent enmasse ; 3) les abeilles, dont la recherche auhasard a été infructueuse retournent à laruche, et obtiennent, des butineuses, qui ren-trent chargées, l’information sur la locali-sation de la source.Les différences entre les deux espèces peu-vent peut-être s’expliquer par la différencede leurs milieux naturels : M. quadrifas-ciatavit dans la végétation dense de la forêtpluviale atlantique du Brésil, où les arbres defloraison massive peuvent être plus abon-dants ou plus faciles à rencontrer que dansune forêt ouverte, qui est l’habitat deM. scutellaris. Une recherche faite plus oumoins au hasard peut suffire à M. quadri-fasciata.

Melipona abeille sans aiguillon / butinage/ recrutement / communication animale /direction et distance

Zusammenfassung – Rekrutierungsver-halten bei stachellosen Bienen (Meliponascutellarisund Melipona quadrifasciata).I. Sammeln an Futterquellen in unter-schiedlicher Richtung und Entfernung.In der Absicht, sensorische Mechanismendes Rekrutierungsverhaltens stachelloserBienen zu analysieren (siehe Begleitartikel,[5]), muβte zunächst zweifelsfrei festge-stellt werden, ob die beiden untersuchtenArten, Melipona scutellarisund M. quad-rifasiata, Sammelbienen zu einer bestimm-ten Futterstelle rekrutieren oder nicht. Füralle Experimente wurden fünf markierteSammlerinnen zu einem Futterplatz trainiert(max. Entfernung 140 m, Abb. 1). DreiStunden lang wurden alle Neuankömmlingean der Futterquelle und einer Kontrollfut-terquelle, die sich nur bezüglich der Rich-tung vom oder der Entfernung zum Stock

Résumé – Comportement de recrutementdes abeilles sans aiguillon, Melipona scu-tellaris et Melipona quadrifasciata. I. Buti-nage à des sources de nourriture situéesdans des directions et à des distancesvariables. Cherchant principalement à étu-dier les mécanismes sensoriels impliquésdans le comportement de recrutement desabeilles sans aiguillon (voir l’article asso-cié [5]), nous avons d’abord voulu établirde façon certaine si les deux espèces étu-diées Melipona scutellariset Melipona qua-drifasciatarecrutaient ou non des butineusespour une source de nourriture donnée. Pourchaque expérience nous avons dressé cinqbutineuses marquées à venir visiter un nour-risseur distant de 140 m au maximum de laruche (Fig. 1). Durant trois heures nousavons prélevé toutes les nouvelles venuessur le nourrisseur test et sur le nourrisseurtémoin, qui différait l’un de l’autre soit parla distance, soit par la direction. A l’aide dutest χ2 (niveau de signification p ≤ 0,05)nous avons testé la répartition des abeillessur les deux nourrisseurs par rapport auhasard.Les deux espèces recrutent bien des congé-nères du nid pour une source de nourriturebien approvisionnée. Chez M. scutellarisladirection (jusqu’à 140 m, Fig. 2a) est com-muniquée plus précisément que la distance(jusqu’à 30 m, Fig. 3a), alors que chezM. quadrifasciatala direction n’est com-muniquée que jusqu’à 30 m (Fig. 2b) et ladistance jusqu’à 40 m (Fig. 3b). Chez lesdeux espèces le recrutement comporte deuxphases : dans la phase initiale les congé-nères mises en alerte cherchent la nourri-ture au hasard ; dans la seconde phase, lesabeilles qui quittent la ruche possèdent visi-blement l’information sur la localisationspécifique de la nourriture. En conséquence,au bout de 35 min pour M. scutellariset85 min pour M. quadrifasciata, les nou-velles venues arrivent en plus grand nombresur le nourrisseur test (Fig. 4). Ce résultatsuggère la succession suivante d’événe-ments : 1) quand une butineuse découvreune source de nourriture bien approvisionnée,

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von der Futterquelle unterschied, gesam-melt. Mit Hilfe des χ2– Tests (Signifikanz-niveau: p ≤ 0.05) wurde die Verteilung derBienen an den beiden Futterstellen auf ihreZufälligkeit überprüft.

Sammelbienen beider Arten können ihreStockgenossinen zu einer lohnenden Fut-terstelle rekrutieren. Bei M. scutellariswirddie Richtung einer Futterquelle bis zu einerEntfernung von 140 m (Abb. 2a) von denSammlerinnen genauer übermittelt als derenEntfernung (bis zu 30 m, Abb. 3a). BeiM. quadrifasciatahingegen wird die Rich-tung einer Futterquelle lediglich bis 30 mangegeben (Abb. 2b), die Entfernungenjedoch bis zu 40 m (Abb. 3b). Der Zeitver-lauf der Sammelaktivität zeigt bei beidenArten zwei Phasen. In der ersten Phase ver-lassen von Sammlerinnen alarmierte Bie-nen den Stock ohne Information über denOrt der Futterquelle. In der darauffolgen-den Phase jedoch verfügen die Sammelbie-nen über die entsprechende Information:nach 35 Minuten (M. scutellaris) bzw. 85Minuten (M. quadrifasciata) fliegen signi-fikant mehr Bienen zur Futterquelle als zurKontrollfutterquelle (Abb. 4). UnsereBefunde sprechen für die folgende Sequenzder Ereignisse: (i) findet eine Sammelbieneeine lohnende Futterquelle, übermittelt sieim Stock Information über den Duft und dieQualität des Futters. (ii) Alarmierte Stock-genossinnen suchen daraufhin ungerichtetnach einer entsprechenden Futterquelle. Intropischen Wäldern könnte diese Strategieausreichen, um Massenblüher erfolgreichauszubeuten. (iii) Bienen, die während die-ser Zufalls-Suche erfolglos blieben, kehrenin den Stock zurück und erhalten von erfolg-reichen Sammelbienen Information überden Futterstandort.

Die Verhaltensunterschiede zwischenM. scutellarisund M. quadrifasciataerklärensich möglicherweise aus Unterschieden ihrernatürlichen Lebensräume: M. quadrifasciatalebt in der dichten Vegetation des Brasilia-nischen Atlantischen Regenwaldes, M. scu-tellaris hingegen in weit offeneren Wäldern.

Massenblüher sind im dichten Regenwaldhäufiger anzutreffen als in offenem Wald-gelände. Eine Suchstrategie, die mehr oderweniger auf Zufall beruht, könnte somitgerade fürM. quadrifasciataausreichen.

stachellose Bienen / Sammelverhalten /Rekrutierung / Richtungskommunika-tion und Entfernungskommunikation /Melipona

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