Hydrochus armatus, 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 : 359-362

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Hydrochus armatus

new species

Hydrochus armatus , new species

Figs. 1 View FIGURE 1 , 2 View FIGURE 2

Type Material. Holotype (male): “ Ecuador: Napo Province, Limoncocha, on Rio Napo 10-IV-1974 Boyce A. Drummond, III blacklight trap ” ( NMNH) . Paratypes (2): Same data as holotype (1 NMNH) ; Napo Province, Limoncocha , (1°33’S, 75°35’W), 12.vi.1977, leg. W. E. Steiner (1 NMNH) GoogleMaps .

Differential Diagnosis. Among Ecuadorian species, recognized by the combination of moderate size (ca. 4.10 mm), the moderately deep pronotal impressions, and the distinctive male genitalia, which have the parameres strongly scleotized and, in dorsal/ventral views widened at midlength, in addition to the strongly sclerotized aedeagus ( Fig. 2 View FIGURE 2 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males.

Description. Habitus as illustrated ( Fig. 2 View FIGURE 2 ). Size: holotype (length/width, mm): body (length to elytral apices) 4.10/1.42; head width 0.97; pronotum l/w 0.94/1.03; PA 0.90; PB 0.84; elytra 2.55/1.42. Body size moderate (ca. 4.10 mm). Dorsum grey to greenish grey, with slight to moderately strong iridescence, elytra with black spots. Punctation on elytra ca. 2–3x that of pronotum. Elytra interstriae ca. 1–1.5x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th moderately raised, moderately elongate.

Pronotum slightly wider than long, widest slightly behind anterior margin, narrowed at base, sides arcuate or very weakly sinuate, smooth; anterior margin slightly bisinuate; anterior depressions deeper than posterior, reliefs lateral to anterior depressions rounded.

Elytra with spaces between strial punctures narrow walls to ca. 1x their diameter; apices conjointly rounded in dorsal view, in lateral view outer margin with very slight angulation.

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

Male genitalia ( Fig. 2 View FIGURE 2 ) general characters: Genitalia very large, strongly sclerotized, with margins between strongly sclerotized areas and weakly or non-sclerotized areas very distinct; parameres longer than aedeagus, plsa small, parameres in dorsal/ventral views with middle 1/3 widened and strongly sclerotized, in lateral view parameres much wider, pointed apically, with two moderately large pwsa; aedeagus lanceolate, with alsm, apex sharply pointed; basal piece slightly shorter than parameres, dorsal margin arcuate in lateral view, orifice strongly sclerotized.

Dorsal surface: adbl moderately large; adtl at about distal 1/3.

Ventral surface: avtl at about proximal 1/5 of aedeagus.

Etymology. Named in reference to the shape and sclerotization of the male genitalia.


Smithsonian Institution, National Museum of Natural History