Hydrochus bucapitus, Perkins, 2020

Perkins, Philip D., 2020, Taxonomy of Peruvian water beetles in the genus Hydrochus Leach, 1817 (Coleoptera: Hydrochidae), Zootaxa 4868 (1), pp. 61-89 : 69-71

Hydrochus bucapitus , new species

Figs. 1 , 6

Type Material. Holotype (male): “ PERU: Madre de Dios; Rio Tambopata Res ; 30 air km SW Pto. Maldonado, 290 m, 26–30 xi 1979, J. B. Heppner, subtropical moist forest” ( NMNH) . Paratype: Same data as holotype, except 5 xi 1979 (1 NMNH) .

Differential Diagnosis. Differentiated from other Peruvian species by the combination of the moderate body size (ca. 2.50 mm), the rather large head (width greater than width or length of pronotum), and the male genitalia ( Fig. 6 ; described below). Completely reliable determinations will include dissection of males.

Description. Habitus as illustrated ( Fig. 6 ). Size: holotype (length/width, mm): body (length to elytral apices) 2.50/0.83; head width 0.62; pronotum l/w 0.58/0.55; PA 0.55; PB 0.42; elytra 1.60/0.83. Body size moderate (ca. 2.50 mm), very narrow, except head relatively wide. Dorsum dark brown with slight iridescence, elytra without black spots. Dorsum with numerous microsetae. Legs testaceous, with tibiofemoral joints and basal ½ of femora darker. Punctation on elytra ca. 2–4x that of pronotum. Elytra interstriae narrow walls to ca. 0.5x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th very weakly raised.

Pronotum very slightly longer than wide, widest at anterior margin, narrowed at base, sides very weakly arcuate, almost straight, smooth; anterior margin arcuate; depressions moderately deep, coarsely densely punctate, reliefs between depressions less punctate.

Elytra with spaces between strial punctures narrow walls to ca. 0.5x their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin without angulation.

Ventral characters: Mentum moderately densely finely punctate, with large, deep median fovea. Submentum with two large deep foveae.

Male genitalia ( Fig. 6 ) general characters: genitalia very small, very slender, length ca. 6x width; parameres pointed in dorsal/ventral views and lateral view, only slightly longer than aedeagus, lacking plsa; aedeagus narrowly lanceolate, agw at about midlength; basal piece slightly shorter than parameres, width ca. equal in dorsal/ventral and lateral views, orifice sclerotized, inverted V-shape in dorsal/ventral views.

Dorsal surface: adbl large; pdmm approximating alm.

Ventral surface: pvmm over middle ½ overlapping aedeagus, margins very narrowly separated one from the other.

Etymology. Named in reference to the relatively large head.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURE 6. Hydrochus bucapitus n. sp., habitus and male genitalia of holotype.