Hydrochus formosus, 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 : 17-19

Hydrochus formosus new species

Figs. 2 , 12

Type Material. Holotype (male): “ Venezuela: Guarico State: 8° 8.713’ N, 66° 20.598’ W, 74m, Marsh E of San Nicolasito, 11.i.2009, Expedition Team ; VZ09-0111-01G2” ( MIZA) . Paratypes (102): Venezuela: Amazonas: AS-08-081A (1 SEMC) ; VZ09-0115 - 03 B (2 SEMC) . Apure: AS-06-019 (15 SEMC, MIZA) ; VZ09-0117 - 01X (4 SEMC) ; VZ09-0117 - 03X (1 SEMC) . Bolivar: VZ09-0112-01A (4 SEMC) ; VZ09-0112 - 01 C (1 SEMC) ; VZ09- 0112 - 02 B (1 SEMC) ; VZ09-0113 - 01X (3 SEMC) ; Puerto Ayacucho (66kmN), Rio Horero , 25 Jan 1989, netted, stream edge, Collected by PJSpangler, RAFaitoute & CBBarr (12 NMNH) . Guarico: VZ09-0109- 01X (1 SEMC) ; VZ09-0110 - 01 A (21 SEMC, MIZA, MALUZ) , VZ09-0110 - 02X (17 SEMC) ; VZ09-0111 - 02X (1 SEMC) ; 32 km SW. Calabozo II-11-1969, P. & P. Spangler (18 NMNH) .

Differential Diagnosis. Among Venezuelan species, recognized by the combination of moderately large size (ca. 3.15–4.08 mm), the shallow pronotal depressions, the comparatively long elytra, the lack of an elevation of the 5 th elytral interstria, and the male genitalia ( Fig. 12 ; described below). Additionally, males are recognized by the sharply pointed tubercles, one each on the midline of abdominal ventrites three and four; this appears to be a unique sexual dimorphism in Neotropical Hydrochus . The male genitalia are unique in the pattern of sclerotization of the parameres.

Description. Habitus as illustrated ( Fig. 12 ) Size: holotype (length/width, mm): body (length to elytral apices) 4.04 /1.38; head width 0.96; pronotum l/w 0.85/0.92; PA 0.88; PB 0.85; elytra 2.65/1.38. Body size moderately large (ca. 3.15–4.08 mm). Dorsum grey, with very slight iridescence, elytra with black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 1.5– 2x that of pronotum. Elytra interstriae ca. 2x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Interstria 5 th without elevation or callus.

Pronotum slightly wider than long, widest at or slightly behind anterior margin, narrowed at base, sides sinuate, smooth; anterior margin slightly bisinuate; depressions shallow, only very slightly more densely punctate than low reliefs between depressions.

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 very slight angulation.

Males with sharply pointed tubercles, one each on the midline of abdominal ventrites three and four.

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

Male genitalia ( Fig. 12 ) general characters: paramere tips in dorsal and ventral views arcuate toward midline; in lateral view narrow and tapering, very lightly sclerotized; aedeagus basically lanceolate shaped.

Dorsal surface: pdmm slightly sinuate and at points slightly separated from alm; adbl small.

Ventral surface: each paramere with distinctive sclerotization pattern in distal ½; basal membranous area large; pseudoparameres extending almost to midlength of parameres, rather large in lateral view; avtl distinctive, subapical; basal piece distal membranous area large, with distinctively shaped sclerotization line, produced to point in midline.

Etymology. Named in reference to the pleasing body proportions.

Figures

FIGURE 2. Dorsal habitus of Hydrochus species.

FIGURE 12. Hydrochus formosus n. sp., habitus and male genitalia of holotype.