Acidocerini

Minoshima, Yûsuke & Hayashi, Masakazu, 2011, Larval morphology of the Japanese species of the tribes Acidocerini, Hydrobiusini and Hydrophilini (Coleoptera: Hydrophilidae), Acta Entomologica Musei Nationalis Pragae (suppl.) 51, pp. 1-118 : 12-17

Key to the genera of the tribe Acidocerini from Japan (all instars)

Larvae of the Japanese species of Chasmogenus Sharp, 1882 are still unknown, therefore, we refer to ANDERSON (1976) for the genus; larvae of the genus Megagraphydrus Hansen, 1999 are also still unknown (see Table 1).

1. Mandibles only slightly asymmetrical, both mandibles similar in shape, bearing two inner teeth ( Figs. 30 B–C); ventral surface of abdomen without spinose prolegs. ....................... ................................................................................................. Helochares Mulsant, 1844

– Mandibles strongly asymmetrical, left mandible with one inner tooth, right mandible with two inner teeth ( Figs. 24 C–D); ventral surface of abdomen with spinose prolegs ( Figs. 12 A–B, 28).......................................................................................................................2

2. Nasale serrate on anterior margin, with only one or two lateral teeth ( Fig. 24A ). ............. .................................................................................................. Enochrus Thomson, 1859

– Nasale with more than two distinct teeth, without serrate anterior margin ( Figs. 7C , 10C ). ................................................................................................................................ 3

3. Nasale strongly asymmetrical ( Figs. 7C , 10C ). ............... Agraphydrus Régimbart, 1903

– Nasale almost symmetrical ( ANDERSON 1976: Fig. 9 ). ....................................................... ................................................................................................ Chasmogenus Sharp, 1882

Figures

Fig. 30. Head appendages of Helochares (Helochares) pallens (MacLeay, 1825), first instar. A – antenna, dorsal view; B–C – mandibles, dorsal view; D – maxilla, dorsal view; E – maxilla, ventral view; F – labium, dorsal view; G – labium, ventral view.

Fig. 24. Enochrus (Methydrus) japonicus (Sharp, 1873), second instar.A – clypeolabrum, dorsal view; B – antenna, dorsal view; C–D – mandibles, dorsal view; E – maxilla, dorsal view; F – maxilla, ventral view; G – labium, dorsal view; H – labium, ventral view.

Fig. 12. Agraphydrus narusei (Satô, 1960).A–B – prolegs, ventral view:A – first instar; B – third instar. C–D – shape of setae, dorsal view: C – median part of parietale, third instar, dorsal view; D – thoracic segments, first instar, dorsal view. Seta on PA8 and PA13 missing. Photographs were taken with compound light microscope.

Fig. 7. Head capsule of Agraphydrus narusei (Satô, 1960), first instar. A – dorsal view; B – ventral view; C – detail of anterior margin of head capsule, dorsal view.

Fig. 10. Head capsule of Agraphydrus narusei (Satô, 1960), third instar.A – dorsal view; B – ventral view; C – detail of anterior margin of head capsule, dorsal view.

Fig. 9. Agraphydrus narusei (Satô, 1960), third instar.A – head, dorsal view; B – spiracular atrium, dorsal view.