Hydraena

Perkins, Philip D., 2011, New records and description of fifty-four new species of aquatic beetles in the genus Hydraena Kugelann from South America (Coleoptera: Hydraenidae), Zootaxa 3074, pp. 1-198 : 49

Hydraena d-concava, new species

Figs. 92 (habitus), 95 (aedeagus), 198 (map)

Type Material. Holotype (male): Peru : Cuzco, Quita Calzone Rd. (at km 164), stream, elev. 1030 m, 13° 9' S, 71° 22' W, 3 ix 1989, R. A. Faitoute (colln. 19). Deposited in the USNM.

Differential Diagnosis. A finely punctate species with dorsal interstices and mentum and postmentum strongly shining. The pronotum is entirely brown, without a hint of a macula, and the elytra have a large, diffusely margined macula. Similar in dorsal habitus and ventral structure (including the very deep, inverted V-shaped, median depression of the metaventrite) to H. clystera ( Figs. 91–92 ); differentiated therefrom by the slightly larger size (ca. 1.32 vs. 1.28 mm), the lack of a pronotal macula, and the more distinct metaventral plaques. Males of H. d-concava have straight tibiae, whereas those of H. clystera are arcuate; enlargements of the protibiae also differ in the two species. The aedeagi of the two species, while differing markedly in details, show some general plan similarities, being quite simple in structure, and having the gonopore located at the apex of the distal piece ( Figs. 94– 95).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.32/0.55; head 0.20/0.31; pronotum 0.34/0.39, PA 0.33, PB 0.35; elytra 0.77/0.55. Dorsum of head dark brown to piceous; pronotum brown, without hint of macula; elytra dark brown with large, diffusely margined brown macula across ca. middle 1/3; legs brown; maxillary palpi testaceous, tip not darker.

Frons finely sparsely punctate, punctures slightly larger and much denser near eyes, ca. 1xef, than medially; interstices strongly shining, ca. 1xpd laterally, 2–7xpd medially. Clypeus microreticulate laterally, very finely sparsely punctulate medially. Mentum and postmentum very sparsely very finely punctulate, strongly shining. Genae raised, shining, without posterior ridge.

Pronotum subcordiform, weakly arcuate laterally; anterior margin straight behind eyes, emarginate behind frons, scintilla absent; very finely sparsely punctate, punctures on disc ca. 2xpd those medially on frons, interstices strongly shining, 2–5xpd, punctures slightly larger and denser at anterior and posterior; PF1 absent; PF2 very shallow; PF3 shallow; PF4 absent.

Elytra weakly arcuate laterally; summit of posterior declivity slightly behind midlength; lateral explanate margins moderately wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming finer and more widely spaced toward posterior. Intervals not raised, strongly shining, on basal 1/3 ca. 2–4xpd, as are interstices between punctures of a row, a few punctures subserial. Apices in dorsal aspect rather sharply conjointly rounded, in posterior aspect margins forming very shallow or no angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 3/1/5/5. P1 laminate; median carina sinuate in profile. P2 l/ w ca. 4/3, sides parallel, apex blunt, raised to join equally raised mesoventral intercoxal process. Plaques narrow, straight, very slightly converging toward one another anteriorly, weakly raised, located at sides of very deep, inverted V-shaped, median depression. Metaventrite with very short longitudinal ridge on each side, extended posteriorly from margin of each mesocoxal cavity. AIS width at straight posterior margin ca. 1.5x P2. Protibia straight, medial margin gradually widened from base to ca. distal 2/3, then emarginate to apex, widest point with conspicuous, long seta. Mesotibia straight, medial margin flattened. Metatibia straight, widest at about midlength, distal 1/2 of medial margin with few moderately long stiff setae. Abdominal apex symmetrical; last tergite with apicomedian notch. Females not yet known.

Etymology. Latin, d- (Latin equivalent of the Greek delta, i.e. triangular) plus concava. This name refers to the triangular, concave area of the metaventrite.

Distribution. Currently known only from the type locality ( Fig. 198).

Figures

FIGURE 91. Hydraena clystera, holotype, dorsal and lateral habitus, and venter.

FIGURE 92. Hydraena d-concava, holotype, dorsal and lateral habitus, and venter.