Chasmogenus Sharp, 1882

Smith, Rachel R. & Short, Andrew Edward Z., 2020, Review of the genus Chasmogenus Sharp, 1882 of northeastern South America with an emphasis on Venezuela, Suriname, and Guyana (Coleoptera, Hydrophilidae, Acidocerinae), ZooKeys 934, pp. 25-79 : 25

Chasmogenus Sharp, 1882

Chasmogenus Sharp, 1882: 73.

Differential diagnosis.

Moderately sized beetles, elongate oval in dorsal view, moderately dorsoventrally compressed, 2.5-6.2 mm in total length. Dorsal coloration from light tan-yellow to very dark brown. Ground punctation of the head fine to moderately coarse, labrum with slightly finer ground punctation and almost indistinguishably small systematic punctures that bear long golden setae along the distoanterior margin. Anterior margin of labrum slightly concave medially. Systematic punctures present on the clypeus, pronotum, and elytra. Elytra with very fine to coarse ground punctation and five loosely organized longitudinal rows of sparsely setose systematic punctures, sometimes only distinguishable by presence of setae; with sharply impressed sutural striae. Antennae with eight (Neotropical species) or nine antennomeres (Old World species). Maxillary palps half as long to longer than width of head posterior to eyes. Anterior half of mentum depressed with anteromedial notch, notch variable from shallowly rounded to triangular. Prosternum pubescent, form variable from evenly smooth to moderately tectiform. Mesoventrite either weakly elevated into medial longitudinal carina, or strongly elevated into posteroapical tooth. Metaventrite with median ovoid glabrous region, extending ca. half to slightly more than half the length of the metaventrite and ca. twice as long as it is wide. Metafemora densely and uniformly pubescent basally with a distal glabrous region of variable proportion. Abdomen densely and uniformly pubescent with golden to light yellow setae. Fifth abdominal ventrite with rounded posteromedial emargination lined with short, bristle-like setae. Size and form of aedeagus variable.