Hydrochus bituberculatus, 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 : 11

Hydrochus bituberculatus new species

Fig. 7

Type Material. Holotype (male): “ Venezuela: T.F. Amazonas, Puerto Ayacucho (66kmN), Rio Horero , 25Jan1989, netted, stream edge // Collected by PJSpangler, RAFaitoute & CBBarr” ( NMNH).

Differential Diagnosis. Among Venezuelan species, recognized by the combination of moderate size (ca. 3.72 mm), the shallow pronotal depressions, the large elytral punctures, the large elytral tubercles, and the male genitalia ( Fig. 7 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males.

Description. Habitus as illustrated ( Fig. 7 ). Size: holotype (length/width, mm): body (length to elytral apices) 3.72/1.28; head width 0.90; pronotum l/w 0.82/0.82; PA 0.74; PB 0.72; elytra 2.36/1.28. Body size moderately large. Dorsum grey to silver grey, with slight to moderately strong iridescence, elytra with black spots. Legs brown, with tibiofemoral joints darker.

Punctation on elytra ca. 2– 5x that of pronotum. Elytra interstriae ca. 1–1.5x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Callus on 5 th at usual area, very large and prominently raised; 4 th interstriae raised in area anterior to 5 th callus.

Pronotum length and width equal, widest at about anterior 1/4, narrowed at base, sides weakly sinuate, smooth; anterior margin arcuate or slightly bisinuate; punctures small and rather sparse; depressions shallow, more densely punctate than reliefs between depressions.

Elytra with spaces between strial punctures ca. 0.5– 1x their diameter; Punctures becoming very large at summit of posterior declivity; suture rather prominently raised at summit of posterior declivity; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with moderate angulation.

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

Male genitalia ( Fig. 17 ) general characters: paramere tips sub-sagittate, distal ends pointed, lateral margins arcuate, plsa very small, angulate, medial margins of tips weakly arcuate and well separated from lateral margins of aedeagus, most of tips extending beyond aedeagus, in lateral view tips narrow, sharply pointed, arcuate toward dorsad; aedeagus moderately wide at widest point, margins arcuate at midlength, lateral margins weakly sclerotized; basal piece with rim of orifice strongly sclerotized.

Dorsal surface: adtl located slightly distal to midlength of aedeagus; adbl large; pdmm slightly overlapping alm.

Ventral surface: avtl subbasal; pvmm approximating alm, not overlapping.

Etymology. Named in reference to the large tubercles of the elytra, present on the 5 th interstriae.

Figures

FIGURE 7. Hydrochus bituberculatus n. sp., habitus and male genitalia of holotype.

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