INSECTS OF MICRONESIA Diptera: Chironomidae 1 By MASAAKI TOKUNAGA ENTOMOLOGICAL LABORATORY, KyOTO PREFECTURAL UNIVERSITY; KyOTO, JAPAN INTRODUCTION Up to the present time, the Micronesian chironomid fauna has been little known. I (1940) reported nine species from the material collected by Esaki's Micronesian expedition on Saipan, Truk, Kusaie, and Ponape; Johannsen (1946) described three species from the Swezey collection from Guam. No other attempt was made to study Micronesian Chironomidae. It was therefore with great pleasure that I undertook, at the request of W. W. Wirth and J. L. Gressitt, the examination of a large collection of about 9,400 specimens of chironomid midges from various islands and atolls of Micronesia. The United States Office of Naval Research, the Pacific Science Board (National Research Council), the National Science Foundation, and Bernice P. Bishop Museum have made this survey and publication of the results pos­ sible. Field research was aided by a contract between the Office of Naval Re­ search, Department of the Navy, and the National Academy of Sciences NR 160-175. I would like to express my appreciation to J. L. Gressitt, who supported this study by making available the extensive collection of the Chironomidae and by arranging financial assistance for illustrations, and to W. W. Wirth and the late Professor T. Esaki for various kindnesses. I am indebted to the above-mentioned organizations and to the following individuals for collecting Micronesian chironomids: P. A. Adams, R. H. Baker, J. W. Beardsley, R. M. Bohart, C. F. Clagg, J. F. Gates Clarke, B. McDaniel, R. Danziger, T. Downs, H. S. Ducoff, H. S. Dybas, S. Edgar, T. Esaki, F. R. Fosberg, David Frey, D. T. Fullaway, R. J. Goss, J. A. McGouan, J. L. Gressitt, K. S. Hagen, D. G. Hall, W. H. Hatheway, C. B. Keck, Y. Kondo, N. L. H. Krauss, K. L. Maehler, S. Murakami, W. A. Niering, R. G. Oakley, Z. Ono, Y. Oshiro, R. W. L. Potts, 1. La Rivers, C. W. Sabrosky, F. M. Snyder, O. H. Swezey, H. K. Townes, L. D. Tuthill, and R. L. Usinger. I also thank Miss E. Ohtani, Kyoto Prefectural Unive.rsity, who made the drawings and assisted with the manuscript. 1 This represents, in part, Results nf Prnfessnr T. Esaki's Micrnnesian Expeditinns (1936-1940), Nn. 121. - • Fnrmerly Saikyn University. 486 Insects of Micronesia-Vol. 12, No.5, 1964 Chironomids are typical nematocerous Diptera and very closely allied to the Ceratopogonidae, differing mainly in possessing atrophied mouthparts and simple wing vein Ml + 2 • Further details for separating chironomids and cera­ topogonids have been given earlier in this series (1959, vol. 12, no. 3, Diptera: Ceratopogonidae). The morphological terminology used in this report is the same as for the Ceratopogonidae, (op. cit.) except for the following abbrevia­ tions. AR (antennal ratio), ratio of elongate last segment (or last two in Tany· podinae) to short basal segments taken together of male antenna, but excluding scape (first spherical segment); fMCu, posterior fork between wing veins MSH and CUl; fR, anterior fork at bases of radial branches (Rt, R 2 +3, and R H5 ) ; LR (leg ratio), ratio of length of first tarsal segment (basitarsus) to that of tibia; RL-A, relative lengths of antennal segments from basal to ulti­ mate; RL-A8, relative lengths of eight distal antennal segments from basal to ultimate; RL-FT, relative lengths of femur to tibia, usually of fore leg; RL-L, relative lengths of seven segments of leg from femur to last tarsal segment (excluding coxa and trochanter) ; RL-T, relative lengths of five tarsal segments from basitarsus to last, usually of fore leg; RL-V, relative lengths of wing veins R, Rt, RH5, and stem of fMCu. Other symbols of wing veins are the same as given by Freeman (1955) and Tokunaga and Murachi (1959). Relative lengths shown in the text were measured by an ocular micrometer with magnification of 150 X (1 unit = 0.013 mm.) for wing veins and leg segments, and with magnification of 600 X (1 unit = 0.003 mm.) for seg­ ments of antennae and palps, spermathecae, and male hypopygia. Classification of the Chironomidae has been studied by Kieffer (1906­ 1926), Goetghebuer (1912-1942), Thienemann (1915-1944), Malloch (1915), Lenz (1921-1941), Edwards (1922-1938), Pagast (1931-1947), Johannsen (1934-1946), Townes (1945) and Freeman (1955-1959); however, the posi­ tion of some genera and subgenera is still unsettled. The classification adopted in the present report is based on Goetghebuer's system (1936-1944), partially supplemented and modified with that of Edwards (1929) and Freeman (1955­ 1958) . The following symbols are used to indicate the institutions where speci­ mens are deposited: US (United States National Museum), BISHOP (B. P. Bishop Museum), CM (Chicago Natural History Museum), KU (Kyushu University, Fukuoka), and MCZ (Museum of Comparative Zoology). ZOOGEOGRAPHY The results of examining 9,354 specimens of Chironomidae from the Micronesian Islands may be summarized as follows: 1. The Micronesian chironomid fauna is composed of 100 known species, of which 67 are new. Eight species (8 percent) belong to the subfamily Tokunaga-Chironomidae Tanypodinae, 26 (26 percent) to the Orthoc1adiinae, 5 (5 percent) to the Clunioninae, and 61 species (61 percent) to the Chironominae. Species are concentrated in a few genera of each subfamily, such as Smittia (17 percent of total species) of the Orthoc1adiinae; and Chironomus (22 percent), Poly­ pedilum (18 percent), and Tanytarsus (17 percent) of the Chironominae. 2. Subfamilies Podonominae, Diamesinae, and Corynoneurinae are not known from Micronesia at present. Podonominae are recorded from the Holarctic Region, Chilean Subregion, South Georgia, and New Zealand. According to Edwards (1931), Podonomus appears to have its center of dis­ tribution in South America, and it is therefore possible that species of this subfamily may yet be found in Micronesia. Members of the Diamesinae are chiefly Holarctic and continental in distribution, with a few species in Africa and South America, but there seems to be little possibility of any being found in Micronesia. The Corynoneurinae are similar to the Diamesinae in distribu­ tion and habitat, but a little more widely distributed; some species possibly may be found in cold rapid streams of the high mountainous parts. In addition to these subfamilies, there are many genera of the other subfamilies which are rather common in the continental regions, but are rare or absent in Micronesia. 3. The Micronesian Chironomidae is a depauperate group with partial representation of the family and is thus similar to other insect groups on oceanic islands. 4. Marine chironomids are present, though not abundant, in Micronesia. The Clunioninae are marine in habit, except for a few peculiar Hawaiian species. They are represented by five species in Micronesia, though more species of this subfamily may be expected to be found in the future. Some species of Smittia will probably prove to be marine or littoral in habit. Of Tanytarsus, four species are marine: halophilae, maritimus, magnihamatus and pelagicus,. four are possibly marine: esakii, brachyurus, latiforceps, and dybasi. Pontomyia is a characteristic genus adapted to marine life and only found in the Pacific Ocean. One species, P. oceana, is now known in Micronesia, but P. natans Edwards, described from Samoa and also found in Japan, should be in Micronesia, although not collected there yet. SYSTEMATICS FAMILY CHIRONOMIDAE Delicate, non-biting midges. Head usually flattened, mouthparts reduced, mainly represented by a pair of labella and usually five-segmented maxillary palps, ocelli absent; male antennae strongly plumose and bushy, except in Clunioninae, the maxi­ mum number of segments 15 (Tanypodinae); female antennae never plumose, usually much shorter and with fewer segments than in male (often equal number of segments in Tanypodinae). Legs long and slender, especially fore leg; in Tanypodinae and Or­ thoc1adiinae tibial spurs present on all legs and fore tibia longer than basitarsus; in 488 Insects of Micronesia-Vol. 12, No.5, 1964 Distribution of Micronesian Chironomidae MICRONESIAN ISLAND GROUPS Caroline aco co Other 'k co "'"a- 'ii .. a :':0 .~ -;; ... Localities 0" ~ "co " 'a ::>l a '"c ...co :9" 0 .. :;;< 0 .. '" = ~ (3 I:Q vi Po< >< U 8 Po< = ::>l Tanypodinae 1. Clinotanypus guamensis* Gt 2. Pentaneura (Penta- neura) ponapensis* X X 3. P. (P.) ignobilis X Sumatra 4. P. (P.) delosa XX X Sumatra 5. P. (P.) carolinensis* G XX X 6. P. (Ablabesmyia) monilis X Europe, N. America, Sumatra, Formosa, Asia Minor, cen- tral Asia, Japan 7. Anatopynia boninensis* X 8. A. elongata* G XX X Orthoc1adiinae 9. Metriocnemus Ravellus* XX 10. M. c1aggi* X XX 11. M. adjecta* XX XXX 12. Cricotopus gressitti* X 13. C. sabroskyi* X 14. C. quadrizonatus* X 15. C. sp. No.1 X 16. Orthoc1adius sp. No.1 X 17. Nanoc1adius sp. No.1 X 18. Smittia brevicornis* XX 19. S. setiforceps* X 20. S. palauensis* X 21. S. dupla*' X X 22. S. kraussi* X X X 23. S. triangula* X X 24. S. yapensis* XX X 25. S. micronesiana* X X X 26. S. zonata* X XXX XX 27. S. insulsa X X 28. S. tuberculifera* X G X XXX 29. S. guamensis* G 30. S. bicinctura* X 31. S. postcinctura* X 32. S. fusivenosa* X * Described as new. t Guam only. Tokunaga-Chironomidae Distribution of Micronesian Chironomidae MICRONESIAN ISLAND GROUPS Caroline co "co Other 'C OJ ~ co ",,::::'" Localities 0:: :l :'::3 .~ ..c .. ."l " " 'a ~ co ~< '"co ~ " 0 OJ .. 0 :l :e I'Q en il< '" U f-<" il<" ~ ;;l'" (3 - ->< 33. S. sp. No.1 X 34. S. sp. No.2 X Clunioninae 35. Clunio pacificus XX Japan proper, Ryu- kyu Is., Samoa 36. C. tuthilli* X 37. Thalassomyia maritima XX X New Caledonia, China (Hong Kong) 38.