Hydraena nitidimenta, 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 : 37-38

Hydraena nitidimenta , new species

( Figs. 43 , 45, 452 )

Type Material. Holotype (male): Eastern Highlands Province: Koma River , tributary of Fio River , at rattan bridge crossing, ca. 2.6 km N by W of Herowana airstrip, washed from wet gravel at edge of large rainforest stream, 1400 m, 6° 36' S, 145° 11' E, 29 v 2004, N. Porch ( ANIC) . Paratypes (57): Gulf Province: Marawaka , near Ande, 1000 m, 7° 3.598' S, 145° 44.375' E, 10 xi 2006, Balke & Kinibel ( PNG 89) (30 MCZ, NHM, NMW, PNG, ZSM) ; Sandaun Province: May River , ex river side pool, 970 m, 4° 49.779' S, 141° 38.174' E, 19 x 2003, K. Sagata (WB 41) (1 ZSM) ; Mianmin , river, 700 m, 4° 52.858' S, 141° 31.706' E, 21 x 2008, S. Ibalim ( PNG 197) (1 ZSM) ; Mianmin , river,, 1080 m, 4° 55.78' S, 141° 38.185' E, 24 x 2008, S. Ibalim ( PNG 195) (22 MCZ, NHM, NMW, PNG, ZSM) ; Western Highlands Province: Lugup River , 1700 m, 5° 17.237' S, 144° 28.214' E, 4 iii 2007, Kinibel ( PNG 143) (3 ZSM) .

Differential Diagnosis. The habitus is similar to that of H. jubilata ( Figs. 42 , 43 ); differing therefrom by the shallow pronotal foveae PF2, among other characters (see H. jubilata diagnosis). The shape of the pronotum differs from that of H. lassulipes and H. supina ( Figs. 46 , 47 ); however, the metaventral plaques and the slightly arcuate male metatibiae are quite similar in the three species. The aedeagus ( Fig. 453 ) distinctively differs from that of other members of the Jubilata group, and should be examined for reliable determinations.

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.84/0.71; head 0.29/0.39; pronotum 0.43/0.48, PA 0.41, PB 0.38; elytra 1.13/0.71.

Dorsum dark brown to piceous, except anterior ca. 1/6 of pronotum light brown, legs brown to slightly reddish brown; maxillary palpi brown to light brown.

Frons punctures ca. 1xef; interstices shining, 1–4xpd. Clypeus microreticulate laterally, very finely sparsely punctate medially. Mentum and postmentum similarly nearly impunctate, strongly shining. Genae weakly raised, shining, without posterior ridge. Pronotum cordiform, anterior margin emarginate; punctures on disc ca. 1xpd those of frons, interstices shining, 1–5xpd, punctures much larger and denser at anterior and posterior; PF1 united to form shallow transverse impression across anterior 1/3 of pronotal disc, sometimes with nearly imperceptible low midlongitudinal ridge or narrow area lacking punctures; PF2 shallow, oval, oblique, not confluent; PF3 moderately deep; PF4 very shallow.

Elytra with summit of posterior declivity at or very near midlength; lateral explanate margins narrow; on basal 1/3 punctures ca. 1xpd largest pronotal punctures, punctures becoming gradually smaller toward posterior. Intervals not raised, shining, on disc ca. 2–3xpd, 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. 2/1/3.5/1.5. P1 laminate; median carina sinuate in profile. P2 raised, l/w ca. 2/1, sides slightly converging toward apex, apex joined to mesoventral midlongitudinal ridge. Plaques moderately wide, parallel, weakly raised, especially at lateral margins, located at sides of deep, median depression. Metaventrite with strong midlongitudinal ridge between mesoventral intercoxal process and median depression. AIS width at straight posterior margin ca. equal to P2. All legs long and very slender. Profemur (male) with small, sharply pointed tubercle next to trochanter; protibia slightly emarginate on medial surface in distal 1/2, emargination with row of setae, apex with small cluster of short stout setae on medial surface. Mesotibia straight. Metatibia slightly arcuate. Male fifth ventrite with pair of pits near midline. Abdominal apex symmetrical; last tergite (male) deeply notched.

Aedeagus ( Fig. 45) main piece, in ventral aspect, with right side characteristically thick-walled and with tiny point apically, left side with much larger angulate lobe; left paramere, in lateral aspect, lobe-shaped in distal 1/3; right paramere lobe-shaped in distal 1/2, setae along lower ventral margin, none at apical angle.

Etymology. "Bright chin"; named in reference to the shining mentum.

Distribution. Currently known from Area 1, widely but sparsely distributed; elevation range 700–1700 m; the rather tight cluster of localities near Mianmin, at 700–1080 m, could be considered in Area 2 ( Fig. 452 ).

Figures

FIGURE 42. Hydraena jubilata, holotype, dorsal and lateral habitus, and venter.

FIGURE 43. Hydraena nitidimenta, holotype, dorsal and lateral habitus, and venter.

FIGURE 46. Hydraena lassulipes, holotype, dorsal and lateral habitus, and venter.

FIGURE 47. Hydraena supina, holotype, dorsal and lateral habitus, and venter.

FIGURES 451–454. Geographical distributions of Hydraena species.