Hydrochus hamulus, Perkins, 2020

Perkins, Philip D., 2020, Taxonomy of Ecuadorian water beetles in the genus Hydrochus Leach, 1817 (Coleoptera: Hydrochidae), Zootaxa 4790 (2), pp. 358-374 : 362

Hydrochus hamulus , new species

Figs. 1 , 3

Type Material. Holotype (male): “ ECUADOR: Napo, Limoncocha , (1°33’S, 75°35’W), 14.vi.1977, leg. W. E. Steiner ” ( NMNH) . Paratypes (24): Same data as holotype (16 NMNH) ; Los Rios, Babahoyo , (1°48’S, 79°32’W), 21.vi.1975, leg. Cohen, Langley, & Monnig (7 NMNH) ; Manabi, Tosagua , 5.iii.1978, leg. J. J. Anderson (1 NMNH) .

Differential Diagnosis. Among Ecuadorian species, recognized by the combination of small size (ca. 1.67 mm), the copper to bluish black metallic dorsal color, the deep and coarsely punctate pronotal impressions, the slightly raised odd numbered elytral interstriae, the large and closely spaced elytral serial punctures, and the male genitalia ( Fig. 3 ; described below).

Description. Habitus as illustrated ( Fig. 3 ). Size: holotype (length/width, mm): body (length to elytral apices) 1.67/0.61; head width 0.43; pronotum l/w 0.39/0.42; PA 0.42; PB 0.34; elytra 1.03/0.61. Body size small (ca. 1.67 mm). Dorsum copper to bluish black metallic, with strong iridescence, elytra without black spots. Punctation on elytra ca. 2–3x that of pronotum. Elytra interstriae narrow walls to ca. 1x strial puncture diameter. Interstria 9 th slightly more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th without callus.

Pronotum length slightly wider than long, widest at anterior margin, narrowed at base, sides straight or very slightly arcuate, smooth; anterior margin markedly arcuate; depressions deep, much more densely punctate than reliefs between depressions, latter almost entirely impunctate.

Elytra with odd numbered intervals slightly raised, spaces between strial punctures narrow walls to ca. 0.5x their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin without angulation.

Ventral characters: Mentum densely punctate, with median fovea. Submentum with two foveae. Legs testaceous, femora darker than tibiae.

Male genitalia ( Fig. 3 ) general characters: Genitalia very small, rather wide in both dorsal/ventral and lateral views; parameres longer than aedeagus, tips in dorsal/ventral views gradually tapering to rounded distal end, in lateral view abruptly tapering to rounded distal end; basal piece longer than parameres, basal orifice ventral surface produced in hook-shaped process, most discernable in lateral view.

Dorsal surface: pdmm overlapping lateral margin of aedeagus; adbl absent; adtl absent or not discernable; basal piece with large membranous area, margin U-shaped.

Ventral surface: pvmm sinuate, overlapping aedeagus, especially in distal 1/2; avtl at about proximal ¼ of aedeagus.

Etymology. Named in reference to the hook shape of the basal piece orifice of the male genitalia.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURE 3. Hydrochus hamulus n. sp., habitus and male genitalia of holotype.