Hydrochus velatus, 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 : 38-39

Hydrochus velatus , new species

Figs. 2 , 19 , 59

Type Material. Holotype (male): “ BRAZIL: Matto Grosso, Corumba, F. Plaumann ” ( NHMUK) . Paratypes: Same data as holotype (2 NHMUK) .

Differential Diagnosis. Among Brazilian species, recognized by the combination of moderate size (ca. 3.34 mm), the shallow pronotal depressions, and the male genitalia ( Fig. 19 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 3.34/1.18; head width 0.81; pronotum l/w 0.73/0.79; PA 0.73; PB 0.62; elytra 2.06/1.18. Habitus as illustrated ( Fig. 19 ). Body size moderate (ca. 3.34 mm). Dorsum dark brown to dark grey, with slight or no iridescence, elytra without black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2x that of pronotum. Elytra interstriae ca. 0.5–1x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th very slightly raised.

Pronotum length and width ca. equal, widest at anterior margin, narrowed at base, sides very weakly sinuate, smooth; anterior margin slightly bisinuate; depressions shallow, much more densely punctate than low reliefs between depressions, latter almost entirely impunctate.

Elytra with spaces between strial punctures ca. 0.5–1x their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with slight angulation.

Ventral characters: Mentum punctate, with central depression; submentum with two large foveae.

Male genitalia ( Fig. 19 ) general characters: genitalia elongate, length ca. 5x greatest width, basal piece and parameres ca. same length; paramere tips and aedeagus tip at same level, paramere tips arcing toward midline, tips widely separated, plsa absent, lateral margins of tips weakly arcuate; in lateral view parameres wide basally, narrow from ca. midlength to rounded apex; pseudoparameres large, distal end slightly past midlength of parameres; aedeagus wide in both dorsal/ventral and lateral views, in dorsal/ventral views almost parallel-sided for most of length, narrowing near base, alw just distal to adbl, agw at ca. proximal 1/3; basal piece in dorsal/ventral views tapering from distal end to base, in lateral view also tapering toward base, very slightly arcuate, greatest width in dorsal/ventral views slightly greater than lateral width, orifice large, slightly asymmetrical.

Dorsal surface: adtl not apparent; medial part of parameres very thin, velum-like, pdmm slightly sinuate, separated from alm over ca. distal 2/3, proximal 1/3 turning toward midline and going beneath alm; adbl moderately large.

Ventral surface: avtl not apparent; pvmm slightly wider than pdmm in distal ½, otherwise approximating pdmm.

Etymology. Named in reference to the very thin, velum-like medial margins of the parameres.

Figures

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

FIGURES 18–19. Habitus and male genitalia of holotypes. 18. Hydrochus pronotulus n. sp. 19. Hydrochus velatus n. sp.

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