Hydraena bicarina, Perkins, 2014

PERKINS, PHILIP D., 2014, A revision of the water beetle genus Hydraena Kugelann for southern Africa (Coleoptera: Hydraenidae), Zootaxa 3758 (1), pp. 1-92 : 77-81

Hydraena bicarina , new species

Figs. 55 (habitus), 57 (aedeagus), 69 (map)

Type material. Holotype (male): South Africa: Western Cape Province, Gifberg Pass , 31° 46' S, 18° 46' E, 2 i 2005, P. S. Cranston ( TMSA) . Paratype: Same data as holotype (1 TMSA) .

Differential diagnosis. Differentiated from other members of the group by the elytral sculpture, which has intervals 2, 4, 6 and 8 slightly raised, dull, but with interval 10 more distinctly carinate ( Fig. 55 ). The aedeagus ( Fig. 57 ) distinctively differs from other members of the group. In the two specimens available, each dorsal puncture has a short but rather distinctive seta. The metaventral plaques are slightly shorter than in the other members of the group (ratios 2/1.5/8/4).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.83/0.75; head 0.28/0.44; pronotum 0.41/0.54, PA 0.45, PB 0.43; elytra 1.13/0.75.

Dorsum of head dark brown to piceous; pronotum brown around margins, very slightly darker on disc; elytra dark brown; legs and maxillary palpi brown. Dorsum coarsely densely punctate, each puncture with short but distinctive seta.

Frons punctures ca. 3–4xef; interstices narrow walls, dull. Clypeus coarsely densely punctate, punctures slightly smaller than those of frons. Mentum and postmentum densely coarsely punctate; mentum with shallow basomedian depression. Genae raised, densely, irregularly punctate, dull, with posterior ridge.

Pronotum laterally slightly emarginate in front of middle, more distinctly so behind middle; anterior margin straight behind eyes, shallowly emarginate behind frons, scintilla absent; coarsely densely punctate, punctures on disc slightly larger than those of frons, separated by narrow walls; PF1 shallow, confluent in midline; PF2 moderately deep; PF3 and PF4 deep.

Elytra moderately widely arcuate laterally; summit of posterior declivity at ca. midlength; lateral explanate margin moderately wide; on basal 1/3 punctures ca. 1xpd of largest pronotal punctures, punctures becoming slightly finer and more widely spaced toward posterior. Intervals 2, 4, 6 and 8 slightly raised, dull; interval 10 more distinctly carinate; interstices on basal 1/3 narrow walls to 0.5xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins do not form angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 2/1.5/8/4. P1 slightly wider than laminate; median carina very low, very weakly sinuate in profile. P2 l/w ca. 3/1, sides converging toward narrow apex, apex raised slightly above mesoventral intercoxal process. Plaques large, converging toward one another anteriorly, moderately raised, located at sides of moderately deep median longitudinal depression. Metaventrite with depression lateral to each plaque; without midlongitudinal carina between intercoxal process and median depression. AIS subtriangular, deeply concave, width at slightly arcuate posterior margin ca. 2x P2. All tibiae slender, straight. Abdominal apex symmetrical; last tergite without apicomedian incision.

Etymology. Named in reference to the elytral carinae, one on each 10th interval.

Distribution. Currently known only from the type locality ( Fig. 69 ).

Notes. The smooth, shining area on the elytra of the holotype ( Fig. 55 ) is an artifact, apparently due to damage of some sort; the paratype, which is teneral, does not have this shiny area. The holotype is missing both maxillary palpi; the paratype has only the right palpus.

Figures

FIGURE 55. Hydraena bicarina, holotype, dorsal and lateral habitus.

FIGURES 56–57. Aedeagi of holotypes.

FIGURES 66–70. Geographical distributions of Hydraena species.