Key to the New World species of the Helochares subgenus Hydrobaticus

1. Elytra with distinct rows of serial punctures, sometimes deeply impressed into grooves (e.g., Fig. 2A, C–E). Size variable (4.2– 6.6 mm). Widely distributed............................................................................. 2

- Elytra without rows of serial punctures (Figs. 2B, 4). Size larger than 5.5 mm. Mexico and Central America.............. 8

2. Abdominal pubescence sparse and not uniformly distributed on each ventrite (Fig. 6A). Abdominal ventrites uniformly very dark brown to almost black in coloration. Elytra with rows of serial punctures not impressed into striae............................................................................................ H. normatus (LeConte) (in part)

- Abdominal pubescence dense and uniform, not appearing sparse or absent on anterior half of each ventrite (e.g. Fig. 6 B–D). Abdominal ventrites variously colored. Elytra with rows of serial punctures impressed into striae or not................. 3

3 Size larger (> 5.8 mm). Elytral serial punctures not impressed into striae or only very weakly so; absent or almost appearing absent anteromedially (Fig. 2A).............................................................. H. trujillo n. sp.

- Size variable (4.2–6.0 mm). Elytra with rows of serial punctures impressed into striae or not; rows distinctly present anteromedially............................................................................................... 4

4 Abdominal ventrites pale in color, either uniformly yellowish brown or yellowish brown on lateral thirds with median third darker brown......................................................................................... 5

- Abdominal ventrites uniformly dark brown to almost black in color..............................................6

5 Parameres of aedeagus truncate at apex, with outer corners widely rounded (Fig. 7 F–H). More southern distribution (Panama, Ecuador, Venezuela)....................................................................... H. nexus n. sp.

- Parameres of aedeagus with apex oblique to truncate, with outer corners widely rounded (Fig. 8). More northern distribution (this rarer form known from Mexico)............................................ H. normatus (LeConte) (in part)

6 Clypeus pale in coloration, not darkened medially (Fig. 5A). Eastern North America............. H. maculicollis Mulsant

- Clypeus distinctly darkened medially (Fig. 5E, H). South America............................................... 7

7 Pronotum almost entirely darkly colored (Fig. 2D). Size smaller (4.7–4.8 mm). Ecuador ................ H. zamora n. sp.

- Pronotum only darkened on central disc (Fig. 2E). Size larger (5.2–5.5 mm). Peru ............................ H. sp. A

8 Clypeus pale in coloration, not darkened medially (Fig. 5G). Aedeagus with median lobe broadly rounded, with only a small “pinched” apex (Fig. 7K)............................................................... H. championi Sharp

- Clypeus distinctly darkened medially (Fig. 5I). Aedeagus with median lobe tapered to a point at apex (Fig. 7 I– J)......... 9

9 Aedeagus with apex of parameres rounded (Fig. 6I); lateral outer margins of parameres parallel, slightly constricted near midlength; maximum width of aedeagus at basal half, nearly as wide as maximum width of aedeagus at apical half................................................................................................... H. politus n. sp.

- Aedeagus with apex of parameres truncate (Fig. 6J); lateral outer margins of parameres parallel along basal two thirds, slightly constricted at two thirds, diverging along apical third; maximum width of aedeagus at basal half, clearly narrower than maximum width of aedeagus at apical half........................................................... H. laevis n. sp.