Hydrochus parvicollis, Perkins, 2020

Perkins, Philip D., 2020, Taxonomy of Peruvian water beetles in the genus Hydrochus Leach, 1817 (Coleoptera: Hydrochidae), Zootaxa 4868 (1), pp. 61-89 : 77

Hydrochus parvicollis , new species

Figs. 1 , 11

Type Material. Holotype (male): “ PERU: Madre de Dios; Rio Tambopata Res ; 30 air km SW Pto. Maldonado, 290 m, 6–10 xi 1979, J. B. Heppner, subtropical moist forest” ( NMNH) . Paratypes (4): Same data as holotype (4 NMNH) .

Differential Diagnosis. Among Peruvian species, recognized by the combination of small size (ca. 2.31 mm), the rather small pronotum, head width greater than pronotum width or length, and the male genitalia ( Fig. 11 ; described below). Completely reliable determinations will include dissection of males.

Description. Habitus as illustrated ( Fig. 11 ). Size: holotype (length/width, mm): body (length to elytral apices) 2.31/0.80; head width 0.58; pronotum l/w 0.48/0.54; PA 0.52; PB 0.46; elytra 1.48/0.80. Body size moderate (ca. 2.31 mm). Dorsum grey to bright silver metallic, with moderately strong iridescence, elytra with several black spots. Legs brown to testaceous, with tibiofemoral joints darker. Punctation on elytra deep, ca. 2–3x that of pronotum. Elytra interstriae ca. 1x strial puncture diameter. Interstriae 5 th and 9 th more convex than others, 9 th overhanging 10 th interstria. Usual area of callus on 5 th very slightly raised, if at all.

Pronotum slightly wider than long, widest slightly behind anterior margin, markedly narrowed at base, sides very slightly sinuate, smooth; anterior margin bisinuate; depressions moderately deep, much more densely punctate than reliefs.

Elytra with spaces between strial punctures narrow ridges to ca. 0.5x their diameter; apices rather sharply separately rounded in dorsal view, in lateral view outer margin with very slight angulation.

Ventral characters: Mentum densely punctate, with median fovea. Submentum without foveae.

Male genitalia ( Fig. 11 ) general characters: Male genitalia very small; parameres apically arcuate in ca. 90 degree angle medially directed, distal tips pointed, with pmsm in distal 1/2; aedeagus in dorsal/ventral views with distal 2/3 much wider than parameres, distal end wide and apically truncate, agw at ca. distal 1/3, width narrowed over proximal 1/4; basal piece shorter than parameres, in dorsal/ventral views tapering from distal to base, arcuate in lateral view, orifice damaged during dissection.

Dorsal surface: pdmm overlapping aedeagus basally.

Ventral surface: pvmm produced in lightly sclerotized lobe with minute ridges, overlapping aedeagus

Etymology. Named in reference to the small prothorax, in relation to the size of the head.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURE 11. Hydrochus parvicollis n. sp., habitus and male genitalia of holotype.