Hydraena formosopala, 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 : 117

Hydraena formosopala , new species

( Figs. 210 , 212 , 529 )

Type Material. Holotype (male): East Sepik Province: Prince Alexander Mts. , Wewak, 400 m, 3° 37.319' S, 143° 36.764' E, 21 iv 2006, Balke & Sagata ( PNG 45) ( ZSM) . Paratypes: Same data as holotype (2 ZSM) .

Differential Diagnosis. Similar in pronotal shape (both with PL/PW ca. 0.72), and dorsal sculpture to H. palamita ( Figs. 207 , 210 ); differing therefrom by the much smaller size (ca. 1.29 vs. 1.47 mm), the proportionally shorter elytra (PW/EL ca. 0.57 vs. 0.53), the faint macula on the elytra, and the slightly different plaque ratios (ca. 5/1/5/6 vs. 6/1/6/5). The aedeagi of the two species distinctively differ ( Figs. 209, 212 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.29/0.57; head 0.22/0.31; pronotum 0.31/0.43, PA 0.34, PB 0.36; elytra 0.76/0.57. Head with frons dark brown, clypeus and labrum brown to light brown; pronotum light brown to testaceous; elytra dark brown to reddish brown, with faint light brown macula at posterior declivity; legs light brown; maxillary palpi testaceous, tip not darker.

Frons punctures ca. 1–2xef, 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 emarginate; punctures on disc ca. 1xpd frons punctures, interstices shining, 1–3xpd, punctures slightly larger and denser at anterior and posterior; PF1 very shallow, obsolete; PF2 very shallow; PF3 moderately deep; PF4 absent or very shallow.

Elytra with summit of posterior declivity at or very near midlength; lateral explanate margins moderately 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. 1–2xpd, 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. 5/1/5/6. P1 ca. 2/5 P2; median carina straight in profile; postcoxal process medially concave. P2 transversely concave, l/w ca. 3/5, sides slightly diverging toward blunt apex. Plaques very narrow, carinate, converging slightly anteriorly, at sides of deep median depression. Metaventrite concave between P2 and plaques. AIS width at straight posterior margin slightly greater than P2. All legs moderately long and slender. Profemur (male) without tubercle next to trochanter; protibia slightly arcuate, anterior margin very slightly widened subapically, 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. 212 ).

Etymology. This member of the Pala group has a particularly pleasing body form.

Distribution. Currently known only from the type locality, Wewak, in the Prince Alexander Mts.; this locality is in the eastern extreme of Area 4; elevation 400 m ( Fig. 529 ).

Figures

FIGURE 207. Hydraena palamita, holotype, dorsal and lateral habitus, and venter.

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

FIGURES 212–213. Aedeagi of holotypes. 212. H. formosopala. 213. H. tritropis.

FIGURES 527–530. Geographical distributions of Hydraena species.