Chasmogenus Sharp, 1882

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 : 26

Genus Chasmogenus Sharp, 1882

Note. Two species of the genus Chasmogenus are known from Japan, but immature stages of these Japanese species are unknown. However, judging from a description of C. nitescens ( Fauvel, 1883) from Australia ( ANDERSON 1976, as ‘ Helochares nitescens ’; described mainly according to third instar larvae), the third instar larvae of Chasmogenus should be distinguished from the larvae of remaining Japanese Acidocerini by the following characters: (1) frontal lines V-shaped; (2) clypeolabrum almost symmetrical ( ANDERSON 1976: Fig. 9 ); (3) nasale with five equally large teeth, almost symmetrical ( ANDERSON 1976: Fig. 9 ); (4) mandibles asymmetrical, left mandible with one tooth, right mandible with two teeth ( ANDERSON 1976: Fig. 9 ); (5) abdominal segments with spinose prolegs.

Figures

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