Hydrochus uniformis, 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 : 83-85

Hydrochus uniformis , new species

Figs. 1 , 16

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. 2.27 mm), the dense and deep dorsal punctation, the interstices with sparse to moderately dense microsetae, the pronotal punctures of very uniform size,, and the male genitalia ( Fig. 16 ; described below). Completely reliable determinations will include dissection of males.

Description. Habitus as illustrated ( Fig. 16 ). Size: holotype (length/width, mm): body (length to elytral apices) 2.27/0.86; head width 0.58; pronotum l/w 0.52/0.55; PA 0.52; PB 0.44; elytra 1.36/0.86. Body size moderate (ca. 2.27 mm). Dorsum dark brown to black, with slight iridescence, elytra without distinct black spots. Legs testaceous, with tibiofemoral joints and basal ½ of femora darker. Dorsal punctuation dense and deep. Punctation on elytra ca. 4–5x that of pronotum. Elytra interstriae narrow ridges forming zig-zag pattern to ca. 1x strial puncture diameter, with sparse microsetae. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th weakly raised, moderately elongate, ca. 5 punctures in row on each side.

Pronotum densely coarsely punctate, of quite uniform size; interstices rounded, with rather dense microsetae, length less than width, widest slightly behind anterior margin, narrowed at base, sides arcuate or very weakly sinuate, smooth; anterior margin slightly bisinuate; anterior depressions moderately deep.

Elytra with sutural interval raised over posterior declivity; spaces between strial punctures narrow walls to ca. 0.5x their diameter; apices slightly produced, separately rounded in dorsal view, in lateral view outer margin without angulation.

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

Male genitalia ( Fig. 16 ) general characters: short and rather broad, basal piece longer than parameres; paramere tips extending to level of aedeagus tip, or very slightly beyond, weakly sclerotized, widened slightly, arcuate slightly toward midline but not contacting one another; aedeagus wider than parameres, broad even at base; basal orifice distinctively shaped, broad in lateral view, with apicoventral arcuate process.

Dorsal surface: pdmm contiguous with alm in distal ½, overlapping alm slightly in proximal ½; adtl and adbl absent.

Ventral surface: pvmm slightly overlapping alm; parameres fused to one another basally; pseudoparameres large, ca. ½ length of paramere.

Etymology. Named in reference to the uniform size of the punctures on the head and pronotum.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURE 16. Hydrochus uniformis n. sp., habitus and male genitalia of holotype.