Hydrochus lubricus, Perkins, 2021

Perkins, Philip D., 2021, Taxonomy of Central American water beetles in the genus Hydrochus Leach, 1817 (Coleoptera: Hydrochidae), Zootaxa 4974 (3), pp. 459-503 : 468

Hydrochus lubricus , new species

Figs. 2 , 3 , 39

Type material. Holotype (male): “ MEXICO: Jalisco State, Las Juentas Verano, 17.i.2005, W. D. Shepard leg., Rio Guapinole ” ( SEMC).

Differential diagnosis. Among Mexican species, recognized by the combination of moderate size (ca. 2.30 mm), the deep pronotal impressions, the well raised and very smooth reliefs, and the distinctive male genitalia ( Fig. 3 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males. The distinctive parameres, which are well sclerotized and widened in the proximal ½, are similar in some respects to those of H. armatus Perkins , an Ecuadorian species, but the aedeagal form is very different in the two species.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.98/1.14; head width 0.76; pronotum l/w 0.66/0.76; PA 0.75; PB 0.55; elytra 1.93/1.14. Body size moderate (ca. 2.98 mm). Habitus as illustrated ( Fig. 3 ). Dorsum black with grey to greenish grey strong iridescence, elytra with black spots. Punctation on elytra ca. 1–2x that of pronotum. Elytra interstriae ca. 1–2× 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, ca. 5 punctures in row on each side.

Pronotum wider than long, widest slightly behind anterior margin, narrowed at base, sides sinuate, microdenticulate; anterior margin slightly bisinuate; pronotal depressions, reliefs strongly raised, rounded, very smooth, almost impunctate.

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

Ventral characters: Mentum densely coarsely punctate, disc slightly depressed. Submentum finely punctate, without foveae. Legs brown to dark brown.

Male genitalia ( Fig. 3 ) 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, tips truncate and slightly angled outward, plsa small, rounded; parameres in dorsal/ventral views with middle 1/3 widened and strongly sclerotized, in lateral view parameres much wider, pointed and recurved apically, with two moderately large pwsa; aedeagus narrow, with alsm, apex pointed; basal piece ca. same length as parameres, moderately arcuate in lateral view, orifice sclerotized.

Dorsal surface: adbl large; adtl at about distal 1/4.

Ventral surface: avtl not apparent.

Etymology. Named in reference to the raised, rounded, and very smooth pronotal reliefs.

Figures

FIGURE 2. Dorsal habitus of Central American Hydrochus species.

FIGURES 3–4. Habitus and male genitalia of holotypes. 3. Hydrochus lubricus n. sp. 4. Hydrochus argutoides n. sp.

FIGURES 37–39. Geographical distribution maps.