Hydrochus distinctulus, Perkins, 2021

Perkins, Philip D., 2021, Taxonomy of water beetles in the genus Hydrochus Leach, 1817, from Bolivia, Brazil and Paraguay (Coleoptera: Hydrochidae), Zootaxa 4994 (1), pp. 1-93 : 24

Hydrochus distinctulus , new species

Figs. 2 , 20 , 57

Type Material. Holotype (male): “ BRAZIL: Bahia, 15 Km. E. Itabuna, VII-3-1969, P. & P. Spangler ” ( NMNH) . Paratypes (85): Same data as holotype (84 NMNH) ; Mato Grosso, Buritis (Ribeirao Confins), 29–31.x.1964, leg. (no collector on label) (1 NMNH) .

Differential Diagnosis. Among Brazilian species, recognized by the combination of moderate size (ca. 3.03 mm), the moderately low and relatively impunctate pronotal reliefs, the dorsum with most of head, and all of pronotum dull grey, most of elytra shiny black, with slight iridescence, and the male genitalia ( Fig. 20 ; described below). The dorsal color is similar to that of H. distinctus , which is a much larger species, with very different male genitalia morphology.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 3.03/1.03; head width 0.74; pronotum l/w 0.66/0.69; PA 0.69; PB 0.59; elytra 1.91/1.03. Habitus as illustrated ( Fig. 20 ). Body size moderate (ca. 3.03 mm). Dorsum with most of head, and all of pronotum dull grey, most of elytra shiny black, with slight iridescence, elytra without black spots. Legs testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 2–5x that of pronotum. Elytra interstriae narrow ridges 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 weakly raised, grey.

Pronotum slightly wider than long (ratio ca. 38/35), widest slightly behind anterior margin, narrowed at base, sides very weakly sinuate, smooth; anterior margin bisinuate; depressions shallow, much more densely punctate than low reliefs between depressions.

Elytra with spaces between strial punctures narrow ridges to ca. 0.5x their diameter; apices rather sharply conjointly rounded in dorsal view, in lateral view outer margin with slight angulation.

Ventral characters: Mentum densely punctate, with basomedian fovea; submentum very finely sparsely punctate, without foveae.

Male genitalia ( Fig. 20 ) general characters: genitalia stout, length ca. 4x greatest width, basal piece much short- er than parameres (ratio ca. 3/5); paramere tips extending beyond aedeagus tip, medial margins beyond aedeagus tip parallel or nearly so, paramere tips tapering and arcing slightly toward midline, plsa absent, lateral margins of tips arcuate; paramere widest part, in dorsal view, slightly narrower than aedeagus; in lateral view parameres wide, tapering to sharply pointed apex; pseudoparameres very short; aedeagus wide, sides sinuate, agw at ca. distal 2/3; basal piece in dorsal/ventral views tapering from distal end to base, in lateral view also tapering toward base, greatest width in dorsal/ventral views greater than lateral width, orifice markedly asymmetrical, ventral margin hookshaped.

Dorsal surface: adtl subapical; pdmm markedly sinuate, widely separated; adbl large, width ca. equal to agw.

Ventral surface: avtl near proximal 1/4; pvmm separation much greater than pdmm, overlapping alm only at base.

Etymology. Named in reference to dorsal similarity to the much larger H. distinctus .

Figures

FIGURE 2. Dorsal habitus of Hydrochus species in study area.

FIGURES 20–21. Habitus and male genitalia of holotypes. 20. Hydrochus distinctulus n. sp. 21. Hydrochus fritillus. n. sp.

FIGURES 57–58. Geographical distributions. 57. Endemics and near endemics. 58. H. bituberculatus.