Hydrochus spinosus, 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 : 77-79

Hydrochus spinosus , new species

Figs. 2 , 12

Type Material. Holotype (male): “ PERU: Tambopata Prov., Madre de Dios Dpto, 15km NE Puerto Maldonado, Reserva Cuzco Amazonico , 12°33’S, 69°3’W, 200m, camp, 21 June 1989, J. S. Ashe, R. A. Leschen, #213, ex., at light” ( SEMC).

Differential Diagnosis. Among Peruvian species, recognized by the combination of small size (ca. 1.96 mm), the shallow pronotal depressions, more densely punctate than the low reliefs between depressions, latter almost entirely impunctate, the elytral punctures much larger than the pronotal punctures, and the male genitalia ( Fig. 12 ; described below). Completely reliable determinations will include dissection of males.

Description. Habitus as illustrated ( Fig. 12 ). Size: holotype (length/width, mm): body (length to elytral apices) 1.96/0.69; head width 0.51; pronotum l/w 0.46/0.46; PA 0.46; PB 0.40; elytra 1.23/0.69. Body size small (ca. 1.96 mm), narrow. Dorsum light brown with slight iridescence (holotype is teneral), elytra without black spots. Dorsum with numerous microsetae. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 3–5x that of pronotum. Elytra interstriae narrow walls to ca. 0.5x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th very weakly raised.

Pronotum length and width equal, widest at anterior margin, narrowed at base, sides very weakly arcuate, almost straight, smooth; anterior margin arcuate; depressions shallow, coarsely densely punctate, reliefs between depressions almost impunctate.

Elytra with 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 moderately densely punctate, with small, deep median fovea. Submentum large, with two large deep foveae.

Male genitalia ( Fig. 12 ) general characters: genitalia very small; parameres much longer than aedeagus, tips arcuate toward midline, distal ends pointed; four pseudoparameres, two short and two much longer, the latter with numerous short spines on distal ends; aedeagus widest subapically, basal 2/3 parallel sided or nearly so; basal piece much shorter than parameres, oval in dorsal/ventral views, much narrower in lateral view.

Dorsal surface: aedeagus overlapping pdmm.

Ventral surface: medial margins of large pseudoparameres overlapping lateral margin of aedeagus.

Etymology. Named in reference to the spinose pseudoparameres.

Figures

FIGURE 2. Dorsal habitus of Hydrochus species.

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