Hydrochus simplicatus, 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 : 368-369

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Hydrochus simplicatus

new species

Hydrochus simplicatus , new species

Figs. 1 View FIGURE 1 , 7 View FIGURE 7

Type Material. Holotype (male): “ Ecuador: Napo Province, Limoncocha, on Rio Napo, elev. 300 m, 10.ix.1974, Boyce A. Drummond, III blacklight trap ” ( NMNH).

Differential Diagnosis. Among Ecuadorian species, recognized by the combination of moderate size (ca. 3.58 mm), the moderately low pronotal reliefs, the relatively small, rather sparse pronotal punctures, the numerous dorsal microsetae, and the male genitalia ( Fig. 7 View FIGURE 7 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males.

Description. Habitus as illustrated ( Fig. 7 View FIGURE 7 ). Size: holotype (length/width, mm): body (length to elytral apices) 3.58/1.36; head width 0.88; pronotum l/w 0.82/0.85; PA 0.76; PB 0.70; elytra 2.15/1.36. Body size moderate (ca. 3.58 mm). Dorsum dull grey, with numerous microsetae, without iridescence, elytra with black spots. Punctation on elytra ca. 3–5x that of pronotum. Elytra interstriae ca. 1–2x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th well raised, moderately elongate, elytra transversely humped in this area, posterior declivity rather abrupt.

Pronotum slightly wider than long, widest slightly behind anterior margin, narrowed at base, sides arcuate or very weakly sinuate, smooth; anterior margin arcuate or very slightly bisinuate; depressions shallow to moderately deep.

Elytra with spaces between strial punctures ca. 1x their diameter; apices conjointly rounded in dorsal view, each with single deep oval puncture, in lateral view outer margin with distinct angulation.

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

Male genitalia ( Fig. 7 View FIGURE 7 ) general characters: genitalia wide compared to length; parameres much wider in lateral than dorsal/ventral views, in dorsal/ventral views tips narrow, almost parallel sided, arcuate toward midline, not expanded, without plsa, but with narrow pmsm, in lateral view tapering to very small, weakly recurved distal ends; aedeagus lanceolate, wide, widest at about midlength, tapering from midlength to pointed apex, distal ½ with narrow alsm; basal piece shorter than parameres, ratio ca. 65/40, basal orifice asymmetrical, sclerotized.

Dorsal surface: adtl at about midlength, membranous area distal to adtl large; adbl small; pdmm overlapping aedeagus in basal ½.

Ventral surface: avtl at about basal ¼; pvmm slightly overlapping proximal 1/2 of aedeagus.

Etymology. Named in reference to the comparatively simple male genitalia.


Smithsonian Institution, National Museum of Natural History