COLEOPTERA, Linnaeus, 1758

Hendrich, Lars & Balke, Michael, 2004, Aquatic Coleoptera Of Singapore: Species Richness, Ecology And Conservation #, Raffles Bulletin of Zoology 52 (1), pp. 97-145 : 102

KEY TO THE FAMILIES OF SINGAPORE AQUATIC COLEOPTERA

(True and Phytophilous Water Beetles, adults only)

1. Head prolonged into a beak .............................. Curculionidae

– Head not prolonged into a beak ............................................ 2

2. Middle and hind legs much shorter than forelegs, broad and paddlelike. Eyes completely divided into a dorsal and a ventral eye. ........................................................................... Gyrinidae

– Middle and hind legs not remarkably shorter than forelegs. Eyes usually not divided. If divided, then body of beetle strongly arched in lateral view (only genus Amphiops ) ...................... 3

3. Hind tarsi 4-segmented, third segment bilobed (genus Donacia ) ............................................................................. Chrysomelidae

– Hind tarsi 5-segmented, third segment not bilobed ............. 4

4. Antennae club-shaped ............................................................ 5

– Antennae not club-shaped ..................................................... 7

5. Small, elongated beetles, length <2.5 mm. Body in lateral view appearing rather flat. Abdomen with 6 or 7 ventrites .................................................... Hydraenidae : Genus Hydraena

– Beetle usually larger than 2.5 mm, body oval. In lateral view usually at least dorsally more or less convex or arched. Abdomen with 5 ventrites, or with 5 th ventrite short and emarginate so that an invaginated segment becomes visible, producing the impression of presence of a sixth ventrite (only Berosus ) ................................................................................................... 6

6. Beetle with dorsal tubercles. Anterior margin of head (i.e. anterior margin of clypeus) distinctly emarginate with anterior corners upturned; labrum strongly deflected (not seen from above) .................................................................... Spercheidae

– Beetle without dorsal tubercles. Anterior margin of clypeus rarely emarginate, with anterior corners never upturned; labrum usually visible from above, rarely strongly deflected ............................................................................. Hydrophilidae

7. Metacoxa elevated ..................................................... Noteridae

– Metacoxa not elevated ............................................ Dytiscidae