Hydrochus mesoamericanus, 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 : 468-469

Hydrochus mesoamericanus , new species

Figs. 1 , 6 , 36

Type material. Holotype (male): “ MEX. Aguascalientes Sierra Fria about 40 mi. SW Rincon de Romos, iii.9.1953, #54 8200’ I.J. Cantrall ” ( FSCA) . Paratype: Belize: Cayo District, nr Teakettle Bank, Pook’s Hill , (17°13’N, 88°51’W), 6.i.2003, leg. C. R. Bartlett (1 SEMC) .

Differential diagnosis. Among Central American species, recognized by the combination of moderate size (ca. 3.44 mm), the rather uniformly densely punctate pronotum, except less dense on reliefs, with deep depressions, the distinctly denticulate pronotum lateral margins, and the male genitalia ( Fig. 6 ; described below). This species has a generalized Hydrochus habitus; reliable determinations will require dissection of males. The male genitalia are differentiated from other Central American species by the combination of nearly straight paramere tips and the large dorsal membranous area of the aedeagus.

Description. Habitus as illustrated ( Fig. 6 ). Size: holotype (length/width, mm): body (length to elytral apices) 3.44/1.53; head width 0.78; pronotum l/w 0.73/0.82; PA 0.78; PB 0.69; elytra 2.38/1.53. Body size moderately large (ca. 3.44 mm). Dorsum dark brown, with very little iridescence, elytra without black spots. Punctation on elytra ca. 2–3x that of pronotum. Elytra interstriae ca. 1–1.5× strial puncture diameter. 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 slightly wider than long, widest slightly behind anterior margin, narrowed at base, sides sinuate, minutely but distinctly denticulate; anterior margin bisinuate; rather uniformly densely punctate, except less dense on reliefs; depressions deep.

Elytra with spaces between strial punctures ca. 0.5–1x their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with moderate angulation.

Ventral characters: Mentum coarsely densely punctate, with large median fovea. Submentum punctate, without foveae. Legs brown.

Male genitalia ( Fig. 6 ) general characters: paramere tips slender and pointed, in lateral view narrower than in dorsal/ventral views and sharply pointed, in dorsal/ventral views with medial margins at apex parallel or nearly so, then arcuate away from midline, narrow proximal to plsa; aedeagus in dorsal/ventral views wide in distal ½, only slightly wider in proximal ½, greatest width as ca. midlength; in lateral view slightly wider in proximal ½, and much wider in membranous distal 1/2; lateral margins of aedeagus sclerotized; basal piece slightly shorter than parameres, tapering proximally, orifice strongly sclerotized.

Dorsal surface: pdmm widely separated, sinuate; adbl large; adtl as about distal 1/3; paramere tips without dorsal sclerotized ridge.

Ventral surface: pvmm approximating lateral margin of aedeagus; avtl near base.

Etymology. Named in reference to the geographical distribution.

Figures

FIGURE 1. Dorsal habitus of Central American Hydrochus species.

FIGURES 5–6. Habitus and male genitalia of holotypes. 5. Hydrochus biexcavatus n. sp. 6. Hydrochus mesoamericanus n. sp.

FIGURES 34–36. Geographical distribution maps.