Chasmogenus Sharp

Clarkson, Bruno & Ferreira-Jr, Nelson, 2014, Four new species and first nominal record of Chasmogenus Sharp, 1882 (Coleoptera: Hydrophilidae) from Brazil, Zootaxa 3765 (5), pp. 481-494 : 493-494

Key to Species of South American Chasmogenus Sharp

Adapted from García (2000)

1 Anterocentral notch on mentum subtriangular to triangular (e.g. Figs. 9–11, 20 and 21)............................. 2

– Anterocentral notch on mentum rounded (e.g. Figs. 13–19)................................................... 4

2 Body length smaller than 3.0 mm (2.7 mm)...............................................… C. rufinasus (Knisch)

– Body length larger than 3.0 mm (3.4–5.5 mm)............................................................... 3

3 General dorsal punctures of elytra and pronotum fine, much smaller than systematic punctures. Parameres notably shorter than median lobe, inner margin slightly emarginated on apical fifth, outer margin subparallel basally. Median lobe thick, apex strongly acuminate (Fig. 23)........................................................... C. fluminensis sp. nov.

– General dorsal punctures of elytra and pronotum moderately coarse, only slightly smaller than systematic punctures. Parameres slightly shorter than median lobe, inner margin emarginated on apical three-tenths, outer margin sinuate. Median lobe narrow, apex slightly acuminate (Fig. 25)................................................ C. ubatuba sp. nov.

4 Anterior clypeal emargination wide with its mesal portion straight (Fig. 30 or García 2000: Fig. 1B).................... 5

– Anterior clypeal emargination narrow, rounded to angulate (e.g. Fig. 28)......................................... 6

5 Apex of parameres rounded, inner margins strongly sinuate in dorsal view; median lobe strongly constrict medially, widening abruptly after this constriction, forming an arrowhead-like apical half (Fig. 22).................... C. sapucay Fernández

– Parameres apex truncated, inner margin of parameres somewhat sinuate; median lobe strongly constrict medially, widening slightly after this constriction, apex lance-like (Fig. 31).......................................... C. australis García

6 Pronotal surface unevenly structured with two large depressions near of anterior margin. Mesoventral carina strongly elevated into a posterior tooth (Figs. 32, 34 and 36 or García 2000: Figs. 2C, D and E). Paramere apex truncated (Figs. 33, 35 and 37 or García 2000: Figs. 3F, G and H).......................................................................... 7

– Pronotal surface evenly structured, without large depressions. Mesoventral carina absent or weakly marked. Paramere apex rounded (Figs. 22–26).................................................................................. 9

7 Ultimate labial palpomeres with two preapical long setae. Mesoventral carina higher than its length, anterior portion not salient, with large and thick apical tooth, straight (Fig. 32 or García 2000: Fig. 2C). Manubrium indistinct. Inner margin of parameres straight (Fig. 33 or García 2000: Fig. 3F)......................................... C. occidentalis García

– Ultimate labial palpomeres with a preapical long seta (e.g. Fig. 12). Mesoventral carina shorter than its length, with anterior portion salient (Figs. 34 and 36 or García 2000: Figs. 2D and E). Manubrium distinct or somewhat distinct. Inner margin of parameres somewhat concave or convex (Figs. 35 and 37 or García 2000: Figs. 3G and H)........................... 8

8 Mesoventral carina with short and narrow posteroapical tooth, straight; anterior portion somewhat inclined anteriad (Fig. 34 or García 2000: Fig. 2D). Inner margin of parameres slightly concave medially (Fig. 35 or García 2000: Fig. 3G).................................................................................................. C. bariorum García

– Mesoventral carina with very small posteroapical tooth directed backward; anterior portion rounded, somewhat blunt anteriad (Fig. 36 or García 2000: Fig. 2E). Inner margin of parameres convex medially (Fig. 37 or García 2000: Fig. 3H)................................................................................................ C. yukparum García

9 Body length larger than 5.0 mm (6.0– 6.2 mm). Anterior clypeal margin rounded, without emargination. General dorsal punctures of elytra and pronotum moderately coarse, only slightly smaller than systematic punctures. Phallobase elongated with manubrium weakly distinct. Inner margin of parameres emarginated on apical fifth, outer margin subparallel to somewhat concave medially. Median lobe constricted medially (Fig. 26)....................................... C. itatiaia sp. nov.

– Body length smaller than 5.0 mm (3.80–4.55 mm). Anterior clypeal margin with rounded emargination, exposing a gap between clypeus and labrum (e.g. Fig. 28). General dorsal punctures of elytra and pronotum fine, much smaller than systematic punctures. Phallobase short with manubrium distinct. Inner margin of parameres slightly emarginated on apical three-tenths, outer margin slightly concave. Median lobe not constricted medially (Fig. 24)....................... C. lilianae sp. nov.