Hydrochus forcipulus, 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 : 27

Hydrochus forcipulus , new species

Figs. 2 , 36 , 55

Type Material. Holotype (male): “ BOLIVIA: Beni, 40 km E. San Borja, Estacion Biologica Beni, Estancia El Porvenir ; 6–8 Sept. 1987; W. E. Steiner // At black light; open grass savanna and marsh” ( NMNH) . Paratypes (2): Bolivia: Beni, 40 km E. San Borja, Estacion Biologica Beni, Palm Camp , (14°44’S, 66°40’W), 10.ix.1987, leg. M. G. Pogue (1 NMNH) ; Beni Stn., Palm Camp, NE. of San Borja , 6–9.viii.1988, leg. Robert W. Brooks (1 NMNH)

Differential Diagnosis. Among Brazilian species, recognized by the combination of small size (ca. 1.95 mm), the grey to black color, the pronotum with very shallow impressions and coarse dense punctuation, the pronotal shape, and the male genitalia ( Fig. 36 ; described below). Differentiation from other similarly small sized species with similarly shaped pronotum will require dissection of males.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.95/0.78; head width 0.53; pronotum l/w 0.50/0.49; PA 0.47; PB 0.43; elytra 1.27/0.78. Habitus as illustrated ( Fig. 36 ). Body size small (ca. 2.36 mm). Dorsum grey, with moderately strong iridescence, elytra without black spots. Legs brown to testaceous, with tibiofemoral joints darker. Punctation on elytra ca. 1–2x that of pronotum. Elytra interstriae ca. 0.5–1x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th not raised.

Pronotum slightly wider than long (as ca. 15/16), widest at anterior margin, markedly narrowed at base, sides very slightly arcuate, smooth; anterior margin bisinuate, with fringe of short setae over lateral 1/3; depressions very shallow; punctation coarse and dense.

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 moderately coarsely punctate, median fovea shallow; submentum without foveae.

Male genitalia ( Fig. 36 ) general characters: genitalia very narrow, elongate, length ca. 6x greatest width, parameres longer than basal piece (ratio ca. 19/15); parameres tapering to very fine apices, very narrow and extending well beyond distal end of aedeagus, medial margins beyond aedeagus tip diverging slightly one from the other, plsa absent, in dorsal/ventral views lateral margins of tips straight; in lateral view paramere tip very thin and arcuate ventrad, sharply pointed apically; aedeagus moderately wide, agw at ca. midlength; basal piece in dorsal/ventral views with slightly arcuate lateral margins, in lateral view arcuate, dorsal surface more arcuate than ventral, maximum width in dorsal/ventral views slightly greater than lateral width, orifice asymmetrical, margin sclerotized.

Dorsal surface: adtl at ca. midlength of aedeagus; pdmm slightly overlapping alm in proximal ½, otherwise approximating alm; adbl small.

Ventral surface: avtl at ca. midlength of aedeagus; pvmm overlapping alm in proximal 1/3, medial margins very narrowly separated.

Etymology. Named in reference to the forceps-like male genitalia.

Figures

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

FIGURES 36–37. Habitus and male genitalia of holotypes. 36. Hydrochus forcipulus n. sp. 37. Hydrochus forcipuloides n. sp.

FIGURES 55–56. Geographical distributions. 55. Endemics and near endemics. 56. H. bicarinatus and H. merkli.