Hydrochus basilaris, Perkins, 2019

Perkins, Philip D., 2019, Taxonomy of Venezuelan water beetles in the genus Hydrochus Leach, 1817, and an analysis of male genitalia morphology (Coleoptera: Hydrochidae), Zootaxa 4708 (1), pp. 1-59 : 26-28

Hydrochus basilaris new species

Figs. 1 , 17

Type Material. Holotype (male): “ Venezuela: Bolivar State: 4° 37.362’ N, 61° 5.679’ W, 876m, Gran Sabana, N. Santa Elena, Rio Guara at Rt. 10, 17.vii.2010, leg. Short, Tellez & Arias; marshy area; VZ10-0717-02A” ( MIZA) . Paratypes (9): Venezuela: Bolivar: Same data as holotype (9 SEMC, MIZA) .

Differential Diagnosis. Among Venezuelan species, recognized by the combination of moderate size (ca. 2.54– 3.31 mm), the moderately shallow pronotal depressions, and the male genitalia ( Fig. 17 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males. The aedeagus is narrow and almost straight-sided for most of length, but has a very large adbl; the parameres are distinctively subsagittate, with emarginate inner margins over the distal 1/3, and have distinctive pwsa.

Description. Habitus as illustrated ( Fig. 17 ). Size: holotype (length/width, mm): body (length to elytral apices) 3.18/1.09; head width 0.76; pronotum l/w 0.70/0.73; PA 0.70; PB 0.64; elytra 2.03/1.09. Body size moderate (ca. 2.54–3.31 mm). Dorsum grey, with slight to moderately strong 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 very slightly raised.

Pronotum slightly wider than long, widest slightly behind anterior margin, narrowed at base, sides arcuate or very weakly sinuate, smooth; anterior margin arcuate or slightly bisinuate; depressions moderately deep, much more densely punctate than 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 very slight angulation.

Ventral characters: Mentum coarsely punctate, with median fovea. Submentum with two foveae.

Male genitalia ( Fig. 17 ) general characters: paramere tips sub-sagittate, distal ends pointed, lateral margins straight, not emarginate, plsa obtusely angulate or slightly rounded, medial margins of tips emarginate (curving away from midline) and well separated from lateral margins of aedeagus, only distal 1/4 of tips extending beyond aedeagus, in lateral view tips narrow, sharply pointed; aedeagus comparatively narrow, with sclerotized lateral margins; basal piece with rim of orifice strongly sclerotized, apicoventrally produced in lobe.

Dorsal surface: adtl located slightly distal to midlength of aedeagus; adbl large, distinctively shaped; pdmm very slightly overlapping alm; pwsa distinctive, oval in dorsal view.

Ventral surface: avtl subbasal, U-shaped; pvmm approximating alm.

Etymology. Named in reference to the very large aedeagus dorsal basal lobe, compared to the comparatively narrow remainder of the aedeagus.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURE 17. Hydrochus basilaris n. sp., habitus and male genitalia of holotype.