P u b l i c a t i o n s s c i e n t i f i q u e s d u m u s é u m

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Santoedited byPhilippe Bouchet, Hervé Le Guyader, Olivier Pascal

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Focus on aquatic insects

Arnold H. Staniczek

Aquatic insects are a heterogeneous assemblage comprising several insect orders which have inde-pendently evolved in aquatic habitats. The larvae of mayflies (Ephemeroptera), damselflies and dragonflies (Odonata), stoneflies (Plecoptera), alderflies and dobsonflies (Megaloptera), and caddisflies (Trichoptera) are obligatory bound to freshwater habitats. Furthermore, the true bugs (Heteroptera), beetles (Coleoptera) and

flies (Diptera) each include many large families present only in aquatic habitats. In fact, almost every insect order has at least a few aquatic representatives. In all kinds of continental fresh-water environments, aquatic insects are usually the largest single group of organisms, by species as well as specimen numbers, and are of para-mount importance to the community structure and function.

in BoucHet P., Le guyAder H. & PAScAL o. (eds), The Natural History of Santo. MNHN, Paris; Ird, Marseille; PNI, Paris. 572 p. (Patrimoines naturels; 70).

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. . . . . . .However, in isolated tropical archipelagos the fau-nal composition of freshwater environments may entirely differ from continental conditions. The dis-persal of aquatic freshwater insects from continents to isolated archipelagos is severely hampered by long distances over sea. Adult mayflies, stoneflies, and caddisflies are poor flyers and delicate insects, so their success in establishing island population is rather limited. A colonisation through larval dispersal can entirely be ruled out, as freshwater insect larvae generally do not survive in marine conditions. While crustaceans, e.g. shrimps, may secondarily conquer freshwater habitats from the seas, all species of insects must bridge the sea either by aerial dispersal or by clinging to driftwood.This is mainly the reason for an entirely different freshwater species composition on Vanuatu com-pared to the Australian or Asian mainlands. In the streams of Santo only a very limited amount of freshwater insects species is present, and regard-ing arthopods the streams are rather dominated by freshwater shrimps.

Mayflies (ephemeroptera) …Larvae of mayflies are easily recognized by the presence of abdominal gills and three tail filaments. The larvae of most species mainly feed on detritus. Adult mayflies do not feed anymore and have a very short life span rang-ing from several hours to a few days. Adult mayflies are characterized by the presence of two or three long tail filaments. The hind wings of mayflies are reduced; in some species they are even completely lost.Kimmins described in 1936 a single species of mayflies from Erromango, but mayflies have never been reported from Santo. During our field work we were able to record three different mayfly spe-cies. The larvae and female adult of Caenis vanuat-ensis (Caenidae) have been described recently. The description of a new species of Labiobaetis as well

as the description of the larva of Cloeon sp. is cur-rently in press.

••• Key for the identification of larvae     of the mayfly families of Vanuatu1-a: All abdominal gills leaf-like, situated on sides of abdomen at least on segments II-VIIBaetidae1-b: Abdominal gill I finger-like, abdominal gills II situated dorsally on abdomen and modified to an operculum covering gills III-VICaenidae

••• Baetidae (small minnow mayflies)Cloeon sp.Labiobaetis sp.Larvae of Baetidae are only of few centimetres length. They have a spindle-shaped body to which six or seven leaf-like pairs of abdominal gills are inserted laterally. The outer tail appendages, the cerci, are only medially fringed with long swim ming hairs. Baetidae mainly feed on detritus. Usually small min-now mayflies have two to three generations within one year.A single species of Baetidae, Cloeon erromangense, is known from Erromango and was described by Kimmins (1936) from adults. We encountered lar-vae of two spe cies of small minnow mayflies in several streams of western Santo. One species can be attributed to Cloeon sp., but as the adults remain unknown it is not clear if these larvae are conspecific with C. erromangense or if they represent a differ-ent species. The other collected species from Santo belongs to Labiobaetis, a genus that is widespread in the Australasian realm. Both genera are very similar to each other and thus not easy to distinguish for laymen. The larvae of Labiobaetis (Fig. 302A) usu-ally have a long and broad medial projection on the second segment of the labial palp and lack gill I. Both species were only collected in calm river parts cling-ing to the riverine vegetation.

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Figure 302: ephemeroptera. a: Labiobaetis sp. B-D: Caenis vanuatensis. (Photos A.H. Staniczek).

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••• Caenidae (small square-gilled mayflies,      angler’s curses)Caenis vanuatensis Malzacher, 2007Caenidae belong to the smallest mayflies, with only a few millimetres of body length. Their adults are char-acterized by the total loss of their hind wings, and the forewings lack marginal intercalary veins. The larval abdominal gills are modified: Gill I is reduced and fin-gerlike, gill II is modified to an operculum that covers gills III-VI, gill VII is lost. The larvae of C. vanuatensis (Figs 302B & 302C) can be distinguished from other species of Caenis by the significantly reduced and shortened dorsal ridge of the operculate gill II.There are more than 100 species of Caenidae described worldwide. While some species are also reported from Indonesia, Papua New Guinea, Australia, and Fidji, they are neither present in New Zealand nor in New Caledonia.C. vanuatensis is abundant in many of the investi-gated streams in both western and eastern Santo. Numerous larvae were collected under stones and on the ground where they feed on detritus. All lar-vae found were of similar size which may point to a synchronised life cycle.All collected larvae and reared adults (Fig. 302D) were of female sex. This makes it likely that C. vanu-atensis is a parthenogenetic species. Parthenogenesis is often assumed to occur more likely on islands, and this phenomenon is also known from other species of Caenidae.

Dragonflies and Damselflies …(odonata)

Adult Odonata are generally more robust and mobile than other aquatic insects. Especially dragonflies are known as agile perchers and thus are very successful in the colonisation of islands. This may be the reason

that a comparatively higher number of species could be found on Santo. The vast majority of Odonata found on Vanuatu is widely distributed throughout Southeast Asia and the Australasian region, but the species of Vanuatubasis are considered endemic to islands of Vanuatu. Until now 25 species of Odonata were known from Vanuatu. In our field studies we recorded 13 species, adding seven new records for Espiritu Santo. Five of these are also new for Vanuatu. Our study thus increases the total number of dragon-flies for Vanuatu to 29, and now 17 species are known from Santo (Table 29).

••• Key for the identification of adults     of the odonate families of Vanuatu1-a: Fore- and hind wings similarly shaped and petio-late. Eyes well separated on top of the head. Discoidal cell four-sided (quadrilateral), never traversed by crossveinsSuborder Zygoptera 21-b: Forewings narrower than hind wings and never petiolate. Eyes touching on top of the head. Discoidal cell three-sided (triangle), sometimes traversed by crossveinsSuborder Anisoptera 3

2-a: Pterostigma distinctly longer than broad. Several wing cells five-sided. Veins IR3 and R4+5 originate far basal to the node. At least one supplementary, interca-lated vein several cells long between branches of Rs in distal portion of wingsFamily Lestidae with one genus: Austrolestes2-b: Pterostigma not or scarcely longer than broad. Most wing cells four-sided. Veins IR3 and R4+5 origi-nate beneath the node. No supplementary longitudi-nal veins between branches of Rs in distal portion of wingsFamily Coenagrionidae with six genera: Agriocnemis, Ischnura, Melanesobasis, Vanuatubasis, Pseudagrion, Trineuragrion

Agriocnemis exsudans Selys, 1877 Kimmins (1936), also as A. vitiensis

Ischnura aurora (Brauer, 1865) Kimmins (1936), as I. torresiana

Vanuatubasis santoensis Ober & Staniczek, 2009 New for Espiritu Santo and Vanuatu

Vanuatubasis sp. New for Espiritu Santo and Vanuatu

Pseudagrion microcephalum (Rambur, 1842) Kimmins (1936)

Pseudagrion sp. New for Espiritu Santo and Vanuatu

Anax guttatus (Burmeister, 1839) Kimmins (1936)

Hemicordulia fidelis McLachlan, 1886 New for Espiritu Santo

Diplacodes bipunctata (Brauer, 1865) Kimmins (1936)

Diplacodes haematodes (Burmeister, 1839) New for Espiritu Santo

Diplacodes trivialis (Rambur, 1842) Kimmins (1936)

Neurothemis stigmatizans (Fabricius, 1775) Kimmins (1936)

Rhyothemis phyllis (Sulzer, 1776) Kimmins (1936)

Orthetrum serapia Watson, 1984 Kimmins(1936), as O. sabina

Orthetrum villosovittatum (Brauer, 1868) New for Espiritu Santo and Vanuatu

Tramea propinqua Lieftinck, 1942 New for Espiritu Santo and Vanuatu

Pantala flavescens (Fabricius, 1798) Kimmins (1936)

table 29: Seventeen species of dragonflies are known from Santo.

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. . . . . . .3-a: Discodial cells in fore- and hind wings similarly shaped and more or less equidistant from arculus. Middle lobe of labium large, lateral lobes widely seperatedFamily Aeshnidae with four genera: Adversaeschna, Anaciaeschna, Anax, Gynacantha3-b: Discodial cells in fore- and hind wings differently shaped and much nearer to arculus in hind wing than in forewing. Middle lobe of labium small and con-cealed by the contiguous lateral lobes4

4-a: Posterior eye margin with prominenceFamily Corduliidae with one genus: Hemicordulia4-b: Posterior margin of eye without a conspicious prominenceFamily Libellulidae with seven genera: Agrionoptera, Diplacodes, Neurothemis, Orthetrum, Pantala, Rhyothemis, Tramea

••• Annotated species list of Odonata from Santo

Damselflies (Zygoptera) - Coenagrionidae

Agriocnemis exsudans Selys, 1877 (Figs 303A, 303B & 303C) (no common name)A. exsudans (syn. A. vitiensis) is a small species of damselflies with hind wings shorter than 14mm. It is found throughout the southwestern Pacific. Adult males are very characteristic, as they are cov-ered with whitish pruinosity on thorax and legs. Young males as well as females do not exhibit any pruinescence, but have an orange-red colouration on abdominal segments VIII-X. Otherwise they are coloured green and black. A. exsudans has been previously recorded from Shark Bay, Espiritu Santo, by Kimmins. It is also recorded from Vila by Tillyard in 1913. We encountered A. exsudans in the area of Tasmate at Taro fields and near Tasmate River. It was also recorded from Penaoru near Penaoru River.

Ischnura aurora (Brauer, 1865) (Fig. 303D) (Aurora bluetail)This species was commonly encountered at tem-porary puddles and ponds in the Tasmate area. Its males are characterized by a green thorax, reddish abdomen with a black tail, additionally marked with blue on segments VIII-IX. It is also a small to tiny species. It occurs from India to the Central Pacific.

Pseudagrion is a large genus with more than 150 described species worldwide. P. microcephalum occurs from the Indian subcontinent through Southeast Asia and northeastern Australia into the western Pacific. It was previously recorded from Shark Bay, Santo. We did however not encounter this species during our field work. P. microcephalum is a medium-sized black and blue damselfly.

Pseudagrion sp. (Fig. 303F)So far this species was unknown from Vanuatu and is recorded herein for the first time. The specimens are pres-ently investigated and cannot yet be clearly assigned to

a certain species. Males of the species found at Penaoru River are predominantly black with dark metallic green mesothorax and blue metathorax. Abdominal segments VIII and IX are almost completely blue.Female specimens are blackish with green thoracic and and abdominal sterna.

Vanuatubasis santoensis Ober & Staniczek, 2009 (Fig. 303E) (no common name)Kimmins (1936, 1958) described Nesobasis male-kulana from Malekula and Nesobasis bidens from Aneityum. Ober & Staniczek 2009 restricted Nesobasis to 21 species described from Fiji, established the new genus Vanuatubasis for the two known spe-cies from Vanuatu, and added another new species Vanuatubasis santoensis from Santo to the new genus. V. santoensis was recorded from the lower courses of Penaoru River, Mamasa River and Paé River. The males of this endemic species have an extraor-dinarily long abdomen, its general colouration is mainly olive green with brown longitudinal tho-racic stripes. Also characteristic is a blue labrum.

Vanuatubasis sp. There is probably at least another species of Vanuatubasis present on Santo. Female specimens were collected that are probably not conspecific with any known species of Vanuatubasis and thus remain undescribed for the moment.

Dragonflies (Anisoptera) - Aeshnidae

Anax guttatus (Burmeister, 1839) (Lesser green emperor)This genus represents large to very large dragonflies. A. guttatus is distributed from India throughout the Pacific. Its light green thorax and abdominal seg-ment I is very distinctive.Abdominal segments II-III are of light blue colour, the remaining abdominal segments are black with pale brown spots. The species has previously been described from Hog Harbour, Santo by Kimmins in 1936. We were not able to catch the species, but have numerous sightings from Tasmate.

Dragonflies (Anisoptera) - Hemicorduliidae

Hemicordulia fidelis McLachlan, 1886The distribution of this species is restricted to New Caledonia, The Loyalties, and Vanuatu. Kimmins reported in 1936 this species from Tanna and (under H. assimilis oceanica) from Aneityum, Malekula, and Efate. We record this species for the first time from the west coast of Santo. Three female specimens were caught from Tasmate River and Penaoru River. Most females of the species can be distinguished from all other Hemicordulia females by the presence of a diffuse amber cloud covering the distal part of the forewing near the pterostigma. Its general appearance is dark green metallic.

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Figure 303: odonata. a-c: Agriocnemis exsudans. D: Ischnura aurora. e: Vanuatubasis santoensis. F: Pseudagrion sp. G: Diplacodes bipunctata. H: Diplacodes haematodes. i: Diplacodes trivialis. J-K: Neurothemis stigmatizans. L: Orthetrum villosovittatum. (Photos M. Pallmann).

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. . . . . . .Malekula and with one male and female specimen from Shark Bay, Santo, by Kimmins. We were not able to encounter the species during our field work. R. phyllis has colourless or tinged yellow wings marked with brownish to black patches. A major brownish black area at the base of the hind wings is traversed by a yellow cross-band. The wing tips are also darkened.

Orthetrum serapia Watson, 1984 (Green Skimmer)O. serapia was found near Tasmate at Mamasa River. Kimmins recorded the closely related O. sabina from East Santo at Shark Bay, but the latter species is otherwise only known from the Palearctic to Australia and New Guinea. Kimmins’ specimens most probably represent O. serapia, which is pos-sibly distributed from the Philippines to the south-western Pacific. The species is characterized by the presence of three light green stripes on the syn-thorax edged with brown. The abdomen is basally swollen and constricted from segment III on.

Orthetrum villosovittatum (Brauer, 1868) (Fig. 303L) (Fiery Skimmer)This species is recorded for the first time for Vanuatu. It was found at Tasmate, Mamasa River, and Penaoru. It is a very distinctive, medium to large sized species with a red abdomen in the male. Females are entirely coloured yellow to orange. The species is distributed in North and Eastern Australia, New Guinea and adjacent islands.

Tramea propinqua Lieftinck, 1942 (Northern Glider)Two mature males of his large dragonfly were found at Tasmate River. These findings rep-resent the first record for Vanuatu. Like all other species of the genus, T. propinqua has conspicuous dark brown patches at the base of the hind wings. In this species these mark-ings are narrow, not reaching the base of the triangle. Additionally, the top of the male frons is metallic purple. T. propinqua is also recorded from Northeast Australia, New Guinea, and the Bismark Archipelago.

Pantala flavescens (Fabricius, 1798)(Wandering Glider, also Globe Skimmer)This species has a large distribution throughout the tropics and warmer temperate regions of the world. It is known to be a strong migrant, and its dispersal is associated with the Inner Tropical Convergence Zone. Kimmins (1936) recorded this species from Hog Harbour and Shark Bay, Espiritu Santo. The medium sized, dull orange to brownish species inhabits a wide range of still waters.

other aquatic insect orders …Plecoptera (stoneflies) have never been recorded from Vanuatu. We have neither been able to con-firm the presence of any species of stoneflies during

Dragonflies (Anisoptera) - Libellulidae

Diplacodes bipunctata (Brauer, 1865) (Fig. 303G) (Wandering Percher)Diplacodes ranges from Africa and Asia through to the Western Pacific. D. bipunctata is found in a variety of still waters and was frequently observed in Taro fields near Tasmate. It was also collected at Tasmate River and Penaoru River. The species was previously also recorded from Banks Island. It is a small to medium-sized, red species. It has a small amber spot at the hind wing base that does not reach the rear margin of the hind wing.

Diplacodes haematodes (Burmeister, 1839) (Fig. 303H) (Scarlet Percher)D. haematodes is very close to the previous spe-cies, but differs from D. bipunctata in having an elongate, light yellow tinged area on the hind wing base, which extends to its rear margin and to the triangle. It is widely distributed and occurs in Australia, Sri Lanka, New Guinea, New Caledonia, and Vanuatu. It has previously been only recorded from Aneityum and Erromanga. D. haematodes was frequently observed in West Santo at Tasmate River, Pai River, and Penaoru River.

Diplacodes trivialis (Rambur, 1842) (Fig. 303I) (Chalky Percher)The distribution of D. trivialis reaches from the Seychelles to Fiji. This species is recorded in Santo for the first time, though it was previously known from Malekula and Erromanga. It inhabits ponds, taro fields, and swampy areas. This species is of predominantly black colour marked with yellow, becoming bluish grey in the mature male.

Neurothemis stigmatizans (Fabricius, 1775) (Figs 303J & 303K) (Painted Grasshawk)This species is frequently observed throughout Santo. It is distributed from India to the western Pacific and inhabits a wide range of still waters. We found this species frequently at Taro fields near Tasmate, and also at backwaters of Mamasa River and Penaoru River. The mature males of N. stigmatizans are easily recognized by their characteristic, large, brownish red wing mark-ings that cover the basal two thirds of the wings. In young males these markings are of brownish yellow colour. The colour of the pterostigma also changes from whitish yellow to red during matu-ration. In females, the pterostigma is also red, but there the otherwise clear wings have only lightly tinged wing markings at the tips and basally of the pterostigma.

Rhyothemis phyllis (Sulzer, 1776) (Yellow-striped Flutterer)This species is distributed from Myanmar to Australia and through the western and south-ern Pacific. It has been previously recorded from

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caddisflies (Trichoptera) at Santo, although Kimmins, Mosely, and Neboiss described several species of Trichoptera from Vanuatu.In some temporary puddles near Penaoru there were also some specimens of water scavenger bee-tles (Hydrophilidae) collected, but their taxonomy has not yet been worked out.

our field work. It is most likely that Plecoptera have not been able to colonise Santo. Stoneflies are also not reported from New Caledonia and many other Southwest Pacific Islands. The same applies to dobsonflies (Megaloptera) who most probably do not occur on Santo.We were also not successful in collecting any

The

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ISSN 1281-6213

ISBN MNHN : 978-2-85653-627-8ISBN IRD : 978-2-7099-1708-7

The islands of the Pacific are renowned for the high levels of endemism of, and threats to, their unique faunas and floras. Espiritu Santo, affectionately known simply as Santo, is an island of superla-tives: the largest and highest in Vanuatu, Santo is an extraordinary geographical and cultural micro-cosm, combining reefs, caves, mountains, satellite islands, and a history of human habitation going back 3 000 years. In the spirit of famous voyages of discovery of the past, the Santo 2006 expedition brought together over 150 scientists, volunteers and students originating from 25 countries. With contributions by more than 100 authors, The Natural History of Santo is a lavishly illustrated homage to the biodiversity of this "planet-island". Bridging the gap between scientific knowledge and conservation and education, The Natural History of Santo was written with local stakeholders as well as armchair naturalists from all over the world in mind.

9 782856 536278 Prix : 59 TTC

Les îles du Pacifique sont célèbres pour le très haut niveau d’endémisme et la grande vulnérabilité de leurs faunes et de leurs flores. L'île d'Espiritu Santo, ou Santo, cumule les superlatifs : la plus grande et la plus haute du Vanuatu, Santo est un extraordinaire microcosme géographique et cultu-rel, avec récifs, grottes, montagnes, îles et îlots satellites, et une occupation humaine qui remonte à 3 000 ans. Renouant avec l'esprit des "Grandes Expéditions Naturalistes", l’expédition Santo 2006 avait mobilisé sur le terrain plus de 150 scienti-fiques, bénévoles et étudiants de 25 pays. Petit tour de force éditorial avec plus de 100 auteurs, ce Natural History of Santo est un éloge de la bio-diversité de cette "île-planète". À la fois beau livre richement illustré et bilan des connaissances scien-tifiques, The Natural History of Santo se veut un outil de connaissance pour sa conservation dura-ble. Il s'adresse autant aux acteurs locaux du déve-loppement et de l'éducation qu'aux naturalistes du monde entier.