Abstract
The Papua New Guinea (PNG) species of the water beetle genus Hydraena Kugelann, 1794, are revised, based on the study of 7,411 databased specimens. The two previously named species are redescribed, and 130 new species are described. The species are placed in 32 species groups. High resolution digital images of all primary types are presented (online version in color), scanning electron micrographs of representative species are given, and geographic distributions are mapped. Male genitalia, representative female terminal abdominal segments and representative spermathecae are illustrated. Papua New Guinea Hydraena species are typically found in sandy/gravelly stream margins, often in association with streamside litter; some species are primarily pond or swamp dwelling, and a few species are usually found in the hygropetric splash zone on stream boulders or on rocks at the margins of waterfalls. The geographic distributions of PNG Hydraena are compared with the Areas of Freshwater Endemism recently proposed by Polhemus and Allen (2007), and found to substantially support those areas. Only one species, H. impercepta Zwick, 1977 is known to be found in both Australia and Papua New Guinea. The probable Australian origins of the PNG hydraenid genera Gymnochthebius and Limnebius are discussed. The origins of just a few species of PNG Hydraena appear to clearly be Australia, and of comparatively recent origin, whereas the origins of the remainder remain problematic because of lack of knowledge of the Hydraena fauna in Papua Province, Indonesia, and islands large and small to the west of New Guinea. No endemic genera of Hydraenidae are currently known for New Guinea, whereas 98% of the known species are endemic.
NSTL