Hydrochus obscurus Sharp

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: 29-32

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Hydrochus obscurus Sharp


Hydrochus obscurus Sharp  

Figs. 2 View FIGURE 2 , 18 View FIGURE 18

Hydrochus obscurus Sharp 1882: 90   .

Hydrochus vanbergehenegouweni Makhan 1992   ; Oliva (1996)

Material examined (65): Venezuela: Aragua: VZ09-0104-01A (1 SEMC)   . Anzoategui: VZ10-0203-03A (1

SEMC). Amazonas: Puerto Ayacucho (66 km N), Rio Horero , 25Jan1989, netted, stream edge, PJSpangler, RA- Faitoute & CBBarr (2 NMNH)   ; Ocamo , 12-IV-1965, F. Fernandez (1 NMNH)   . Apure: AS-06-009 (1 SEMC)   , AS- 06-019 (2 SEMC), VZ09-0118 View Materials - 03X (2 SEMC)   . Barinas: VZ12-0126-01B (2 SEMC)   ; VZ12-0125 View Materials - 02 View Materials A (1 SEMC)   ; VZ12-0125 View Materials - 01 View Materials A (1 SEMC)   . Bolivar: VZ09-0111- 02X (1 SEMC)   . Delta Amacuro: VZ10-0203-01A (1 SEMC)   . Guarico: VZ09-0108- 03X (2 SEMC)   ; Corozo Pando, (8kmN), 11 June 1984, F. W. Eiland II (1 NMNH)   ; Calabozo (44 km S), Hato Masaguaral , 5 Mar 1986, PJSpangler, colln#24 (23 NMNH)   . Sucre: VZ10-0129-04A (24 SEMC)   . Tachira: VZ12-0126-02A (1 SEMC)   .

Differential Diagnosis. Among Venezuelan species, recognized by the combination of moderate size (ca. 2.92– 3.66 mm), the moderately low and relatively impunctate pronotal reliefs, and the male genitalia ( Fig. 18 View FIGURE 18 ; described below). This species has a generalized Hydrochus   habitus; reliable determinations will require dissection of males.

Description. Habitus as illustrated ( Fig. 18 View FIGURE 18 ). Size of illustrated male (length/width, mm): body (length to elytral apices) 3.14/1.17; head width 0.77; pronotum l/w 0.71/0.71; PA 0.69; PB 0.63; elytra 1.94 /1.17. Body size moderate (ca. 2.92–3.66 mm, Venezuelan specimens). Dorsum grey, with slight to moderately strong iridescence, elytra with black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2– 3x 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.

Pronotum length and width equal, or only very slightly wider than long, widest slightly behind anterior margin, narrowed at base, sides arcuate or very weakly sinuate, smooth; anterior margin slightly bisinuate; 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 slight angulation.

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

Male genitalia ( Fig. 18 View FIGURE 18 ) general characters: paramere tips in dorsal and ventral views very weakly sub-sagittate, plsa rounded, lateral margins slightly emarginate, medial margins arcuate toward midline, in lateral view tips narrow and tapering; aedeagus basically lanceolate shaped; basal piece with orifice sclerotized rim produced in small projection on apicoventral margin.

Dorsal surface: adtl at about distal 1/3; adbl moderately size; pdmm overlapping alm.

Ventral surface: aedeagus ventral transition line (avtl) at about proximal 1/3. Paramere medial margins (pvmm) closely approximating aedeagus lateral margins.

Remarks. The specimen imaged ( Fig. 18 View FIGURE 18 ) is from locality VZ12-0126-01B. I have examined the holotype of Hydrochus vanbergehenegouweni Makhan 1992   , including the male genitalia. I concur with Oliva (1996) that Hydrochus vanbergehenegouweni Makhan   is conspecific with Hydrochus obscurus Sharp.  


University of Kansas - Biodiversity Institute


Smithsonian Institution, National Museum of Natural History














Hydrochus obscurus Sharp

Perkins, Philip D. 2019

Hydrochus obscurus

Sharp, D. 1882: 90