Hydrochus panamensis, 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 : 470

Hydrochus panamensis , new species

Figs. 2 , 12 , 28

Type material. Holotype (male): “ Trinidad Riv , Pan. May.21.11, August Busck ” ( NMNH).

Differential diagnosis. Among Central American species, recognized by the combination of large size (ca. 3.95 mm), the deep pronotal impressions, the relatively impunctate pronotal reliefs, the elytra with prominent callus on 5 th interval and raised area of 4 th interval, and the male genitalia ( Fig. 12 ; described below). The male genitalia have a narrow, parallel-sided basal piece, which is narrower than the width of the genitalia at the proximal part of the parameres; these characters plus the shape of the paramere tips serve to differentiate the form from that of other Central American species. This is the largest known Panamanian species of Hydrochus .

Description. Habitus as illustrated ( Fig. 12 ). Size: holotype (length/width, mm): body (length to elytral apices) 3.94/1.42; head width 0.94; pronotum l/w 0.90/0.90; PA 0.87; PB 0.81; elytra 2.52/1.42. Dorsum dark grey, with slight to moderately strong iridescence on head and pronotum, elytra with indistinct black areas. 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 strongly raised, moderately elongate, ca. 5 punctures in row on each side.

Pronotum length and width equal, widest at anterior margin, narrowed at base, sides arcuate, each with unilinear row of minute granules; anterior margin slightly bisinuate; depressions deep, much more densely punctate than distinct reliefs between depressions, latter almost entirely impunctate.

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 without subapical angulation. 4 th interval notably raised from about elytra midlength to level of anterior part of callus on 5 th interval.

Ventral characters: Mentum moderately coarsely punctate, with large, deep median fovea. Submentum with two very shallow foveae. Legs dark brown.

Male genitalia ( Fig. 12 ) general characters: paramere tips slender and pointed, much narrower in lateral view than in dorsal/ventral views, in dorsal/ventral views with medial margins at apex parallel or nearly so, then arcuate away from midline; aedeagus lanceolate, moderately slender in dorsal/ventral views; in lateral view slightly wider basally; lateral margins of aedeagus sclerotized; basal piece slightly shorter than parameres, narrow, much narrower than greatest width of distal pieces, in dorsal/ventral views almost parallel sided, slightly arcuate in lateral view, orifice moderately strongly sclerotized.

Dorsal surface: pdmm sinuate, medial part slightly overlapping aedeagus; adbl moderately large; adtl slightly past midlength.

Ventral surface: pvmm more widely separated than pdmm, approximating lateral margin of aedeagus; avtl very near base; gp large.

Etymology. Named in reference to the geographical distribution.

Figures

FIGURE 2. Dorsal habitus of Central American Hydrochus species.

FIGURES 11–12. Habitus and male genitalia of holotypes. 11. Hydrochus perpunctatus n. sp. 12. Hydrochus panamensis n. sp.

FIGURES 28–30. Geographical distribution maps.