Hydrochus conjunctus, 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 : 55-56

Hydrochus conjunctus new species

Figs. 1 , 31

Type Material. Holotype (male): Venezuela: “ Barinas, Barrancas Research Sta., Rio Yuca , 1 II 1978, 400 ft, seasonal forest, black light, J. B. Heppner ” ( NMNH).

Differential Diagnosis. Among Venezuelan species, differentiated from all others, except H. collaris and H. purpureus , by the deep cervical groove behind the eyes. H. conjunctus is slightly smaller than the other two species, and has a slightly more elongate pronotum. Reliable determination of members of these three species of the collaris group will require dissection of males. In H. conjunctus the aedeagus is widest slightly above midlength, the basal piece is longer and more 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. conjunctus ( Fig. 31 ) are described below.

Description. Habitus as illustrated ( Fig. 31 ). Size: holotype (length/width, mm): body (length to elytral apices) 3.33/1.67; head width 0.81; pronotum l/w 0.81/0.71; PA 0.71; PB 0.57; elytra 2.11/1.67. Body size moderate (ca. 3.33 mm). Dorsum grey, with moderately strong iridescence, elytra with black spots. Legs testaceous to brown, with tibiofemoral joints darker. 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 moderately raised, moderately elongate.

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

Pronotum longer than wide (as ca. 81/71), widest at anterior margin, narrowed at base, sides slightly sinuate, smooth; anterior margin markedly arcuate, fitting into cervical groove; depressions moderately deep, much 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 distinct angulation, impunctate area of apices rather large.

Ventral characters: Mentum densely, moderately coarsely punctate, with shallow median fovea. Submentum with two deep foveae, posterior margin markedly arcuate.

Male genitalia ( Fig. 31 ) 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, tapering slightly from distal end to base, orifice strongly sclerotized, in lateral view “hooking” toward dorsad; aedeagus lanceolate, in lateral view much wider than paramere, lateral margins moderately widely sclerotized, greatest width at about distal 2/3, moderately tapering apically.

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 fit together, forming a strong union.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURE 31. Hydrochus conjunctus n. sp., habitus and male genitalia of holotype.