Hydraena sexsuprema, Perkins, 2011

Perkins, Philip D., 2011, New species (130) of the hyperdiverse aquatic beetle genus Hydraena Kugelann from Papua New Guinea, and a preliminary analysis of areas of endemism (Coleoptera: Hydraenidae) 2944, Zootaxa 2944 (1), pp. 1-417 : 81-82

Hydraena sexsuprema , new species

( Figs. 135 , 137, 494 )

Type Material. Holotype (male): Madang Province: Finisterre Mts., Naho River Valley, Damanti , ex gravel banks of very fast-running clear stream, 914 m, 5° 55' S, 145° 58' E, 11 x 1964, M. E. Bacchus (MEB 47) ( NHM) . Paratypes (93): Madang Province: Finisterre Mts., Lower Naho Valley, Hinggia , ex rocks and gravel bank of swift clear stream, 762 m, 5° 50' S, 146° 7' E, 28 xi 1964, M. E. Bacchus (MEB 112) (73 NHM) ; Finisterre Mts., Naho River Valley, Damanti , ex gravel banks of small fast river, 1082 m, 5° 55' S, 145° 58' E, 8 x 1964, M. E. Bacchus (MEB 37) (10 NHM) ; Finisterre Mts., Naho River Valley, Damanti , ex gravel banks of very fast-running clear stream, 914 m, 5° 55' S, 145° 58' E, 11 x 1964, M. E. Bacchus (MEB 47) (10 NHM) .

Differential Diagnosis. Males differentiated from other species, except the putative sister species H. supersexa , by the strongly arcuate meso- and metatibiae; females recognized by the concave frons ( Figs. 134 , 135 ). Males differentiated from those of H. supersexa by the slightly smaller size (ca. 1.78 vs. 1.86 mm), the less markedly widened tips of the mesotibiae, the presence of a brush of setae on the metatibiae, and the shorter, more widely separated plaques (ratios ca. 4/1/6/8 vs. 4/1/8/6). The male genitalia of the two species share a basic plan, but differ distinctively in shapes of the parameres, among other features ( Figs. 136, 137).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.78/0.72; head 0.28/0.41; pronotum 0.41/0.51, PA 0.43, PB 0.42; elytra 1.08/0.72. Dorsum dark brown to piceous; legs and maxillary palpi dark brown.

Frons markedly microreticulate, except effacedly microreticulate. on middle of disc, punctures ca. 1xef; interstices 1–5xpd. Clypeus microreticulate laterally, finely, moderately sparsely punctate medially. Mentum very sparsely very finely punctulate, strongly shining; postmentum medially micropunctulate, moderately dull. Genae raised, shining, without posterior ridge. Pronotum cordiform, median 2/3 of anterior margin emarginate; microreticulate, more strongly laterally and in PF2 than on disc; punctures on disc ca. 1–2xpd largest punctures of frons, interstices dull, 1–2xpd, punctures slightly larger and denser at posterior; PF1 shallow; PF2 deep, very shallow confluent; PF3 deep; PF4 moderately deep.

Elytra with summit of posterior declivity at or very near midlength; lateral explanate moderately wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, few punctures random near base, punctures becoming gradually smaller toward posterior. Intervals not raised, weakly shining, on disc ca. 1–2xpd, as are interstices between punctures of a row. Apices in dorsal aspect weakly separately rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 4/1/6/8. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 3/2, sides slightly converging toward apex. Plaques carinate, very narrow, located at sides of deep, wide median depression. Metaventrite without midlongitudinal ridge. AIS width at straight posterior margin ca. 1.5x P2. All tibiae strongly arcuate, especially meso- and metatibiae. Profemur (male) with small, sharply pointed tubercle on medial surface short distance from trochanter. Metatibia with brush of setae subapically on medial surface. Abdominal apex slightly asymmetrical; last tergite (male) deeply notched. Aedeagus ( Fig. 137), in ventral view, appearing markedly bent near midlength; left paramere in lateral aspect very wide, with setae along most of margin, ventral margin emarginate.

Etymology. Named in reference to the markedly sexually dimorphic legs and head, and to the relationship to H. supersexa .

Distribution. Currently known from the Naho River Valley in the Finisterre Mts., elevation range 762–1082 m ( Fig. 137). This is in Area 5, but at or very near the border of Area 3.

Figures

FIGURE 134. Hydraena supersexa, holotype, dorsal and lateral habitus, and venter.

FIGURE 135. Hydraena sexsuprema, holotype, dorsal and lateral habitus, and venter.

FIGURES 491–494. Geographical distributions of Hydraena species.