Hydrochus fritillus, 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 : 27-28

Hydrochus fritillus , new species

Figs. 2 , 21 , 59

Type Material. Holotype (male): “ BRAZIL: Matto Grosso side of Rio Araguaia , Santa Isabel // VIII-12 to 22-57, Borys Malkin ” ( NMNH) . Paratype same data as holotype (1 NMNH) .

Differential Diagnosis. Among Brazilian species, recognized by the combination of moderate size (ca. 3.41 mm), the numerous round black dots on the elytra, the pronotal depressions moderately deep, much more densely punctate than the low reliefs between depressions, latter almost entirely impunctate, and the male genitalia ( Fig. 21 ; 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) 3.41/1.15; head width 0.82; pronotum l/w 0.74/0.75; PA 0.72; PB 0.64; elytra 2.18/1.15. Habitus as illustrated ( Fig. 21 ). Body size moderate (ca. 3.41 mm). Dorsum grey to reddish grey, with very slight iridescence, elytra with black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2–3x 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, moderately elongate, ca. 4–5 punctures on each side.

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

Elytra with spaces between strial punctures ca. 1–1.5x 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. 21 ) general characters: genitalia elongate, length ca. 5x greatest width, basal piece shorter than parameres (ratio ca. 11/14); paramere tips extending well beyond aedeagus tip, medial margins beyond aedeagus tip diverging slightly one from the other, plsa absent, lateral margins of tips straight; parameres medial margins in dorsal/ventral views angulate; in lateral view parameres slightly sinuate, sharply pointed apically; aedeagus moderately wide, sides arcuate, agw slightly distal to midlength; basal piece in dorsal/ventral views nearly parallel-sided, in lateral view dorsal surface slightly more arcuate than ventral, maximum width in dorsal/ventral views slightly greater than lateral width, orifice slightly asymmetrical, margin sclerotized.

Dorsal surface: adtl slightly distal to midlength; pdmm sinuate, widely separated, except contacting adbl; adbl large, width ca. equal to agw, in lateral view adbl large, lobate.

Ventral surface: avtl very near base, almost at adbl; pvmm separation greater than pdmm, overlapping alm only at base; gp large.

Etymology. Named in reference to the numerous round black dots on the elytra.

Figures

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

FIGURES 20–21. Habitus and male genitalia of holotypes. 20. Hydrochus distinctulus n. sp. 21. Hydrochus fritillus. n. sp.

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