Hydrochus collaris, 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 : 56-58

Hydrochus collaris new species

Figs. 1 , 32

Type Material. Holotype (male): Venezuela: “T. F. A., blackwater trib. to Maraco River , 3 Feb. 1989, Sta. D., D. A. Polhemus” ( NMNH).

Differential Diagnosis. Among Venezuelan species, differentiated from all others, except H purpureus and H conjunctus , by the deep cervical groove behind the eyes. Compared with other members of the collaris group, H collaris has more convex, impunctate reliefs between the pronotal depressions, and has a larger callus of the 5 th elytral interstria. In H. collaris the aedeagus is widest at distal 3/4, the basal piece is shorter, narrower, and less tapering than that of the compared species, and the adbl is shaped differently: refer also to the diagnosis of H purpureus . Male genitalia of H. collaris ( Fig. 32 ) are described below. Reliable determination of members of these three species will require dissection of males.

Description. Habitus as illustrated ( Fig. 32 ). Size: holotype (length/width, mm): body (length to elytral apices) 3.40/1.17; head width 0.81; pronotum l/w 0.79/0.74; PA 0.74; PB 0.62; elytra 2.13/1.17. Body size moderate (ca. 3.40 mm). Dorsum grey, with moderately strong iridescence, elytra with black spots. Legs with femora reddish brown in basal 2/3 and at tibiofemoral joints, otherwise testaceous; tibiae testaceous. Punctation on elytra ca. 2x 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.

Head with deep curving cervical groove from side to side behind eyes, groove punctate, cervical area behind groove impunctate, shining, with low, closely set longitudinal raised lines.

Pronotum longer than wide (as ca. 79/74), widest at anterior margin, narrowed at base, sides weakly arcuate or very slightly sinuate, smooth; anterior margin markedly arcuate, fitting into cervical groove; depressions moderately deep, much more densely punctate than reliefs between depressions, reliefs between anterior median depression and anterior lateral depressions convex.

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 distinct angulation, impunctate area of apices rather large. Sutural margins raised at summit of posterior declivity.

Ventral characters: Mentum and submentum bright metallic like pronotum. Mentum moderately coarsely and moderately densely punctate, with median fovea; submentum with two large deep foveae, separated by narrow ridge; posterior margin of submentum rather sharply arcuate and raised in middle. Genae on each side with cluster of hairs that overlap antennal groove.

Male genitalia ( Fig. 32 ) general characters: genitalia slender; parameres expanded laterally apically in dorsal/ ventral views, tips wider in dorsal/ventral views than lateral view, extending slightly beyond distal end of aedeagus; basal piece shorter than parameres, narrow, lateral margins almost parallel, orifice strongly sclerotized, in lateral view hooking toward dorsad; aedeagus widened distally, in lateral view much wider than parameres, lateral margins moderately widely sclerotized, greatest width at about distal 2/9, rounded apically; aedeagus internally with midlongitudinal sclerotization in basal 1/2.

Dorsal surface: adtl lacking; pdmm approximating alm; adbl large.

Ventral surface: pvmm basally overlapping alm, margins narrowly separated.

Etymology. Named in reference to the deep cervical groove and the anterior margin of the pronotum, which tightly fit together, forming a strong collar-like union.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURE 32. Hydrochus collaris n. sp., habitus and male genitalia of holotype.