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.