Hydrochus argutus

Perkins, Philip D., 2021, Taxonomy of water beetles in the genus Hydrochus Leach, 1817, from Bolivia, Brazil and Paraguay (Coleoptera: Hydrochidae), Zootaxa 4994 (1), pp. 1-93 : 12

H. argutus species group

Figs. 2 , 5 , 40 , 67 , 70

Members of the H. argutus species group are recognized by the combination of the following characteristics: 1) very small size, length ca. 1.95–2.70 mm; 2) pronotum notably narrowed at base; 3) dorsum densely coarsely punctate, brown or reddish brown, with very slight or no iridescence; 4) elytra apices slightly widened, with sub-marginal groove having large translucent punctures; 5) male genitalia paramere tips appearing sagittate, but only in lateral view, in dorsal/ventral views tips have contiguous medial margins, which extend beyond distal end of aedeagus; parameres slightly longer than basal piece (ratio ca. 15/12), basal piece proximal 1/2 strongly arcuate ventrad, enlarged at orifice. The male genitalia shape is very unusual, and characteristic for the species group. Members include H. argutus ( Brazil, Ecuador, Peru), H. argutulus ( Bolivia) , H. argutissimus ( Venezuela) ( Fig. 67 ), and an undescribed species from Costa Rica (Perkins, in prep.).

Figures

FIGURE 2. Dorsal habitus of Hydrochus species in study area.

FIGURE 5. Dorsal habitus of Hydrochus species in study area.

FIGURE 70. Pictorial aid to species groups of Hydrochus from Bolivia, Brazil and Paraguay, using male genitalia. Not to same scale.

FIGURES 40–41. Habitus and male genitalia. 40. Hydrochus argutulus n. sp., holotype. 41. Hydrochus richteri Bruch.

FIGURES 67–68. Geographical distributions. 67. H. argutus species group. 68. H. cracentis.