Hydrochus robustus, Perkins, 2021

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 : 13

H. robustus species group

Figs. 3 , 26, 27 , 28, 29 , 59 , 71

Members of the H. robustus species group are recognized by the combination of the following characteristics: 1) small to moderate size, ca. 2.10–4.26 mm; 2) male genitalia stout, aedeagus wide in both dorsal/ventral and lateral views, with rounded apex; 3) parameres narrow, apices arcing over aedeagus; 4) pseudoparameres present, in all except H. diffusus , which is tentatively placed in this group. Currently, four species are recognized: H. curvus , H. diffusus , H. radhakishunae , and H. robustus . All four species are only known from southern Brazil and/or Paraguay.

Figures

FIGURE 3. Dorsal habitus of Hydrochus species in study area.

FIGURE 71. Pictorial aid to species groups of Hydrochus from Bolivia, Brazil and Paraguay, using male genitalia. Not to same scale.

FIGURES 26–27. Habitus and male genitalia of holotypes. 26. Hydrochus robustus n. sp. 27. Hydrochus diffusus n. sp.

FIGURES 28–29. Habitus and male genitalia. 28. Hydrochus curvus n. sp., holotype 29. Hydrochus radhakishunae Makhan.

FIGURES 59–60. Geographical distributions. 59. Endemics and near endemics. 60. H. formosus.