Taxonomy of water beetles in the genus Hydrochus Leach, 1817, from Bolivia, Brazil and Paraguay (Coleoptera: Hydrochidae) Author Perkins, Philip D. text Zootaxa 2021 2021-06-28 4994 1 1 93 journal article 10.11646/zootaxa.4994.1.1 1175-5326 5043261 107FCA64-345F-40A4-99D3-5C1441EEAD93 Hydrochus potenspiculatus new species Figs. 1 , 12 , 57 Type Material. Holotype (male): Brazil : Roraima , Caroebe, Rio Jatapú , near Usina de Jatapú , (50.939’N, 59 18.262’W ), 145m , 17.i.2018 , marginal pools of river, Short, BR 18-0117-02A ( INPA ) . Paratypes : Same data as holotype (9 INPA , SEMC ) . Differential Diagnosis. Among Brazilian species, recognized by the combination of moderate size (ca. 3.35 mm ), the grey to bronze dorsum, the pronotal shape, the pronotal depressions shallow to moderately deep, more densely punctate than low reliefs between depressions, latter almost entirely impunctate, the callus on 5 th elytral interseries well raised, and the male genitalia ( Fig. 12 ; 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) 3.35/1.18; head width 0.83; pronotum l/w 0.72/0.77; PA 0.68; PB 0.63; elytra 2.17/1.18. Habitus as illustrated ( Fig. 12 ). Body size moderate (ca. 3.35 mm ). Dorsum grey to bronze, with slight to moderately strong iridescence, elytra with black spots. Legs brown, with tibiofemoral joints darker. Punctation on elytra ca. 3–5x that of pronotum. Elytra interstriae ca. 1–1.5x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th well raised, area between callus and suture slightly concave. Pronotum very slightly wider than long (ratio ca. 40/37), widest slightly behind anterior margin, narrowed at base, sides arcuate, smooth; anterior margin slightly bisinuate; depressions shallow to moderately deep, 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 angulation. Ventral characters: Mentum punctate, with central depression; submentum with two foveae. Male genitalia ( Fig. 12 ) general characters: genitalia large, elongate, length ca. 4.3x greatest width, basal piece shorter than parameres (ratio ca. 5/7); paramere tips extending very slightly beyond aedeagus tip, medial margins beyond aedeagus tip very slightly converging apically, paramere tips sagittate, plsa small, sharply pointed, lateral margins between plsa and apex very slightly emarginate; in lateral view parameres straight, sharply pointed apically; pseudoparameres large, long, almost attaining distal end of parameres; aedeagus moderately wide, agw at about midlength, tapering distally and proximally; basal piece wide, in dorsal/ventral views sides arcuate, tapering basally, slightly wider in dorsal/ventral views than lateral view, in lateral view ventral margin straight, dorsal margin slightly arcuate, orifice very slightly asymmetrical, margin strongly sclerotized. Dorsal surface: adtl at ca. midlength; pdmm well separated, in distals ½, more narrowl separated and overlapping alm in proximal 1/2; adbl small. Ventral surface: avtl at ca. proximal ¼; pvmm more widely separated than pdmm. Etymology . Named in reference to the large and well-muscled basal piece and the very sharply pointed harpoon-like barbs of the parameres.