Hydrochus astrictus, 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 : 66-67

Hydrochus astrictus , new species

Figs. 1 , 4

Type Material. Holotype (male): “ PERU: Tambopata Prov., Madre de Dios Dpto, 15km NE Puerto Maldonado, Reserva Cuzco Amazonico , 12°33’S, 69°3’W, 200m, camp, 9 June 1989, J. S. Ashe, R. A. Leschen, #009, ex., at light” ( SEMC) . Paratypes (35): PERU: Loreto, Pucallpa , 10–12.iv.1969, leg. P. & P. Spangler (11 NMNH) ; Madre de Dios, Rio Tambopata Res ; 30 air km SW Pto. Maldonado, elev. 290 m (13°0’S, 69°33’W), 2–5.xi.1979, leg. J. B. Heppner (4 NMNH) ; same locality, 6–10.xi.1979, leg. J. B. Heppner (2 NMNH) ; same locality, 11–15.xi.1979, leg. J. B. Heppner (4 NMNH) ; same locality, 16–20.xi.1979, leg. J. B. Heppner (8 NMNH) ; same locality, 21–25.xi.1979, leg. J. B. Heppner (3 NMNH) ; same locality, 26–30.xi.1979, leg. J. B. Heppner (3 NMNH) .

Differential Diagnosis. Among known Peruvian species, differentiated from all, except H. bisinuatus , by the deep cervical groove behind the eyes. This species is a member of the H. collaris group (sensu Perkins 2019c); differentiated from H. bisinuatus by the larger body size (ca. 3.00–3.38 vs. 2.74 mm), and the more strongly arcuate anterior margin of the pronotum. However, reliable determinations will require careful examination of the male genitalia ( Fig. 4 ; described below).

Description. Habitus as illustrated ( Fig. 4 ). Size: holotype (length/width, mm): body (length to elytral apices) 3.16/1.10; head width 0.80; pronotum l/w 0.76/0.71; PA 0.71; PB 0.61; elytra 2.08/1.10. Dorsum grey to silver, with moderately strong iridescence, cervical groove black, elytra with black spots. Legs testaceous to brown, with tibiofemoral joints darker. Punctation on elytra ca. 2x that of pronotum. Elytra interstriae ca. 1–2x strial puncture diameter. Interstria 9 th more convex than others, overhanging 10 th interstria. Usual area of callus on 5 th moderately raised, moderately elongate, ca. 6 punctures in row on each side.

Head with deep curving cervical groove from side to side behind eyes, groove punctate, cervical area behind groove impunctate, shining, with very fine, low, closely set longitudinal raised lines.

Pronotum longer than wide (as ca. 76/71), widest at anterior margin, narrowed at base, sides straight or extremely slightly arcuate, smooth; anterior margin sinuate, median ½ markedly arcuate, fitting into cervical groove; anterior angles very slightly produced; depressions moderately deep, more densely punctate than reliefs between depressions.

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 small angulation, impunctate area of apices rather large.

Ventral characters: Mentum coarsely densely punctate, with large, deep median fovea. Submentum with two deep foveae, posterior margin arcuate.

Male genitalia ( Fig. 4 ) general characters: shaft of genitalia long and moderately narrow, basal piece slightly shorter than parameres; paramere tips slightly narrower than aedeagus shaft, medial margins strongly sclerotized, remainder of tips very weakly sclerotized; aedeagus widest at adbl, shaft moderately narrow, margins sinuate, shaft widest slightly before midlength (asgw), then narrowed at about proximal 1/3 of shaft (aslw), then becoming wider before tapering at tip; gonopore on both dorsal and ventral surfaces, the latter much larger than the former; basal piece almost cylindrical, with rim of orifice strongly sclerotized and distinctively hook-shaped.

Dorsal surface: pdmm closely approximating alm, except at adbl; adtl at about midlength of shaft; triangular weakly sclerotized area of paramere very prominent; adbl very large.

Ventral surface: pvmm approximating alm except becoming very narrowly separated from one another and overlapping shaft in proxima1 1/3; gonopore long, distinct, with sclerotized margins in proximal ½.

Etymology. Named in reference to the tightly fitting components of the head and prothorax: cervical groove and anterior margin of the pronotum.

Figures

FIGURE 1. Dorsal habitus of Hydrochus species.

FIGURE 4. Hydrochus astrictus n. sp., habitus and male genitalia of holotype.