Hydraena bicarinova, 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 : 112-113

Hydraena bicarinova , new species

( Figs. 199 , 201, 525 )

Type Material. Holotype (male): Eastern Highlands Province: Wanitabi Valley, nr. Okapa , ex dead leaves caught among rocks in small swift river, 1372 m, 6° 32' S, 145° 37' E, 5 ii 1965, M. E. Bacchus (MEB 171b) ( NHM) . Paratype: Same data as holotype (1 NHM) .

Differential Diagnosis. Similar to H. processa in body proportions and color ( Figs. 198 , 199 ). These two species are the broadest in the Impala group: the EW/TL ratio is ca. 0.48 for H. bicarinova and 0.47 for H. processa (the ratio varies from 0.40 to 0.48 in the group). Hydraena bicarinova differs from H. processa in the slightly finer dorsal punctation, the shallower pronotal foveae PF2, and the slightly wider prosternal intercoxal process (plaque ratios ca. 6/1/5/7 vs. 5/1/5/7). The general plan of the male genitalia of the two species also suggests a relationship, and the genitalia should be examined for reliable determinations ( Figs. 200, 201).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.46/0.70; head 0.21/0.35; pronotum 0.37/0.51, PA 0.39, PB 0.43; elytra 0.89/0.70. Dorsum and legs brown to dark reddish brown; maxillary palpi light brown to testaceous, tip not darker.

Frons punctures ca. 1xef, slightly larger near eyes than medially; interstices shining, 1–3xpd. Clypeus microreticulate laterally, very finely sparsely punctate medially. Mentum and postmentum very sparsely very finely punctulate, shining. Genae raised, shining, without posterior ridge. Pronotum subcordiform, ca. median 3/4 of anterior margin arcuate to posterior; punctures on disc ca. 1xpd frons punctures, interstices shining, 1–3xpd, punctures very slightly larger and denser at anterior and posterior; PF1 very shallow, obsolete; PF2 very shallow, obsolete; PF3 moderately deep; PF4 very shallow.

Elytra with summit of posterior declivity slightly anterior to midlength; lateral explanate margins rather wide; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, a few punctures subserial, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 1–3xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins forming shallow angle with one another.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 6/1/5/7. P1 ca. 1/2 P2; median carina bisinuate in profile. P2 transversely slightly concave, length slightly less than width, sides slightly diverging toward blunt apex. Plaques very narrow, carinate, converging very slightly anteriorly, at sides of very deep median depression. Metaventrite concave between P2 and plaques. AIS width at straight posterior margin ca. 1.5x P2. All legs moderately long and slender. Profemur (male) with very small tubercle next to trochanter; protibia slightly arcuate, distal 1/3 widened anteriorly, medial margin flat except small sharp tubercle subapically on posteromedial margin. Meso- and metatibia straight. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated ( Fig. 210 ).

Etymology. Named in reference to the carinate metaventral plaques and to the ovate body shape. Distribution. Currently known only from the type locality near Okapa, in the eastern part of Area 1; elevation

1372 m ( Fig. 525 ).

Figures

FIGURE 198. Hydraena processa, holotype, dorsal and lateral habitus, and venter.

FIGURE 199. Hydraena bicarinova, holotype, dorsal and lateral habitus, and venter.

FIGURE 210. Hydraena formosopala, holotype, dorsal and lateral habitus, and venter.

FIGURES 523–526. Geographical distributions of Hydraena species.