Hydraena impala, 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 : 106

Hydraena impala , new species

( Figs. 183 , 185 , 534 )

Type Material. Holotype (male): Central Province: nr. Port Moresby, Sogeri Plateau, Musgrave River , ex gravel banks, [GE est.] 100–200 m, 9° 46' S, 147° 41' E, 16 iii 1965, M. E. Bacchus (MEB 200a) ( NHM).

Differential Diagnosis. Similar in color and dorsal sculpture to H. galea ( Figs. 183 , 186 ); differing therefrom by the slightly narrower body form (EW/TL ca. 0.40 vs. 0.45), the narrower mesoventral intercoxal process (P2) (plaque ratios ca. 4/1/5/5 vs. 5/1/5/5), and the micropunctulate mentum. The general plan of the male genitalia of the two species also suggests a relationship, but the genitalia distinctively differ in details, and should be examined for reliable determinations ( Figs. 185 , 188 ).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.36/0.55; head 0.23/0.31; pronotum 0.32/0.45, PA 0.35, PB 0.37; elytra 0.83/0.55. Dorsum of head with frons dark brown to reddish brown, clypeus slightly lighter, labrum testaceous; pronotum brown around ill-defined dark brown macula on disc; elytra dark brown to reddish brown; legs brown to light reddish brown; maxillary palpi 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 micropunctulate, dull. 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 slightly larger and denser at anterior and posterior; PF1 very shallow, obsolete; PF2 very shallow, obsolete; 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. 4/1/5/5. P1 ca. 1/2 P2; median carina very low, bisinuate in profile. P2 transversely concave, l/w ca. equal, sides slightly diverging toward blunt apex. Plaques very narrow, carinate, anteriorly converging very slightly, at sides of deep median depression. Metaventrite concave between P2 and plaques. AIS width at straight posterior margin ca. 1.7x P2. All legs long and slender. Profemur (male) without tubercle next to trochanter; protibia slightly arcuate, anterior margin very slightly widened subapically. Meso- and metatibia straight. Abdominal apex symmetrical; last tergite (male) deeply notched. Aedeagus as illustrated ( Fig. 185 ).

Etymology. Named in reference to the relationship to H. pala , but the absence of the prosternal fovea ("pala") present in that species.

Distribution. Currently known only from the type locality, the Musgrave River, in central Area 11; elevation 100–200 m ( Fig. 534 ).

Figures

FIGURE 183. Hydraena impala, holotype, dorsal and lateral habitus, and venter.

FIGURE 186. Hydraena galea, holotype, dorsal and lateral habitus, and venter.

FIGURES 184–185. Aedeagi of holotypes. 184. H. buloba. 185. H. impala.

FIGURES 531–534. Geographical distributions of Hydraena species.

FIGURES 188–189. Aedeagi of holotypes. 188. H. galea. 189. H. inhalista.