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

Hydrochus obscurus Sharp

Figs. 2 , 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 - 03X (2 SEMC) . Barinas: VZ12-0126-01B (2 SEMC) ; VZ12-0125 - 02 A (1 SEMC) ; VZ12-0125 - 01 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 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males.

Description. Habitus as illustrated ( Fig. 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 ) 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 ) 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.

Figures

FIGURE 2. Dorsal habitus of Hydrochus species.

FIGURE 18. Hydrochus obscurus Sharp, habitus and male genitalia.