Hydrochus clandestinus, 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 : 20

Hydrochus clandestinus , new species

Figs. 1 , 13 , 57

Type Material. Holotype (male): “ BRAZIL: Mato Grosso do Sul; Dois Irmãos do Buriti (c. 5 km NW) on MS- 162 (-20.63497 -55.32535), 308 m, leg. Hamada and team, 27.vi.2018; large pond/lake in cattle field; BR18-0627- 03A” ( INPA) . Paratypes (2 males): Same data as holotype (1 SEMC) . Paraguay: Dep. Cordillera, San Bernadino , 23.vii.1998, leg. U. Drechsel (1 NMW) .

Differential Diagnosis. Among study area species, recognized by the combination of moderate size (ca. 3.30 mm), the shallow pronotal depressions, the moderately low and relatively impunctate pronotal reliefs, and the male genitalia ( Fig. 13 ; 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) 3.30/1.09; head width 0.74; pronotum l/w 0.69/0.75; PA 0.74; PB 0.66; elytra 2.13/1.09. Habitus as illustrated ( Fig. 13 ). Body size moderate (ca. 3.30 mm). Dorsum grey, with slight iridescence, elytra with black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2–3x that of pronotum. Elytra interstriae ca. 1.5–2x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th moderately raised, moderately elongate, ca. five punctures on each side.

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

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 foveae.

Male genitalia ( Fig. 13 ) general characters: genitalia large, elongate, length ca. 4.7x greatest width, basal piece shorter than parameres (ratio ca. 21/47); paramere tips extending well beyond aedeagus tip, medial margins beyond aedeagus tip parallel, plsa very slight, almost absent, lateral margins margins of tips weakly arcuate; in lateral view parameres straight or very slightly arcuate, wide basally, tapering to sharply pointed apex; aedeagus moderately wide, agw at ca. midlength; basal piece in dorsal/ventral views parallel-sided, width in dorsal/ventral views and lateral view ca. equal, in lateral view very slightly arcuate, orifice with dorsal margin transverse, ventral margin with pointed process, process in lateral view hook-shaped.

Dorsal surface: adtl at ca. distal 1/5; pdmm well separated in distal 1/5, remainder sinuate and overlapping alm; adbl very large, rounded laterally.

Ventral surface: avtl not apparent; pvmm more widely separated than pdmm, overlapping alm except for ca. distal ½; gp large.

Etymology. Named in reference to the very generalized Hydrochus habitus.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species in study area.

FIGURES 12–13. Habitus and male genitalia of holotypes. 12. Hydrochus potenspiculatus n. sp. 13. Hydrochus clandestinus n. sp.

FIGURES 57–58. Geographical distributions. 57. Endemics and near endemics. 58. H. bituberculatus.