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

publication ID


publication LSID


persistent identifier


treatment provided by


scientific name

Hydrochus variabilis Knisch


Hydrochus variabilis Knisch  

Figs. 1 View FIGURE 1 , 6B View FIGURES 6 , 14 View FIGURE 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 View FIGURE 14 ; described below). A species with generalized Hydrochus   habitus; reliable determinations will require dissection of males.

Description. Habitus as illustrated ( Fig. 14 View FIGURE 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 View FIGURE 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 View FIGURE 14 ) is from locality VZ10-0202-03A.


Smithsonian Institution, National Museum of Natural History


University of Kansas - Biodiversity Institute


Museo del Instituto de Zoologia Agricola Francisco Fernandez Yepez














Hydrochus variabilis Knisch

Perkins, Philip D. 2019

Hydrochous variabilis

Knisch, A. 1921: 2