Hydrochus variabilis Knisch

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 : 21-23

Hydrochus variabilis Knisch

Figs. 1 , 6B , 14

Hydrochous variabilis Knisch 1921: 2

Material examined (89): Venezuela: Barinas: 10 km NE Barinas , II-23-1969, P. & P. Spangler (8 NMNH) . Bolivar: Upata (69 km SE), 31 Oct. 1982, John L. Hellman (50 NMNH) . Guarico: 15 km S. Calabozo II-9-13-1969, collected in Lago de Los Patos , P. & P. Spangler (17 NMNH) ; 20 km S. Calabozo II-8-13-1969, collected in Rio Orituco , P. & P. Spangler (3 NMNH) ; 12 km S. Calabozo II-6-12-1969, P. & P. Spangler (1 NMNH) ; Calabozo , 15-VII-1961, Biol. Station light trap, C. Bordon leg. (5 NMNH) ; Calabozo II-7-1969, P. & P. Spangler (3 NMNH) . Monagas: VZ10-0202-03A (2 SEMC, MIZA,) .

Differential Diagnosis. Among Venezuelan species, males recognized by the combination of moderate size (ca. 2.85–3.77 mm), the very low and relatively impunctate pronotal reliefs, and the distinctive male genitalia, with elongate paramere tips ( Fig. 14 ; described below). A species with generalized Hydrochus habitus; reliable determinations will require dissection of males.

Description. Habitus as illustrated ( Fig. 14 ). Size of illustrated male (length/width, mm): body (length to elytral apices) 3.42/1.13; head width 0.81; pronotum l/w 0.77/0.79; PA 0.74; PB 0.65; elytra 2.13/1.13. Size ca. 2.85–3.77 mm. Dorsum grey, with slight iridescence, elytra with few black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 1– 2x that of pronotum. Elytra interstriae ca. 1– 2x strial puncture diameter. Interstria 9 th more convex than others, not overhanging 10 th interstria. Usual area of callus on 5 th very slightly raised.

Pronotum slightly wider than long, widest at or just behind anterior margin, narrowed at base, sides arcuate or very weakly sinuate, smooth; depressions very shallow to moderately deep, more densely punctate than very low reliefs between depressions, latter almost entirely impunctate.

Elytral strial punctures ca. 1– 2x size of pronotal punctures, spaces between them 1– 2x their diameter; apices conjointly rounded in dorsal view, in lateral view outer margin with slight angulation.

Male genitalia ( Fig. 14 ) general characters: parameres extending well beyond distal end of aedeagus, tips in dorsal and ventral views nearly same width throughout, medial margins of tips parallel or nearly so, distal ends rounded, slightly oblique, in lateral view tips narrow, distal ends sharply pointed; aedeagus almost parallel-sided,m in lateral view dorsal margin sinuate; basal piece comparatively short and robust, rim of orifice strongly sclerotized.

Dorsal surface: adtl subapical; pdmm overlapping lateral margins of aedeagus, becoming very narrowly separated subbasally; adbl large, distinctively shaped.

Ventral surface: avtl V-shaped, near basal 1/3 of aedeagus; pvmm much more widely separated than pdmm.

Remarks. The specimen imaged ( Fig. 14 ) is from locality VZ10-0202-03A.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURES 6A–C. (A) Male genitalia of H. ducalis Knisch, with parameres spread, showing shape of aedeagus; (B) Male genitalia of H. variabilis Knisch and (C) H. n. sp. from Peru, showing the articulation point of the paramere dorsal basal lobe with the aedeagus dorsal basal lobe.

FIGURE 14. Hydrochus variabilis Knisch, habitus and male genitalia.