Hydraena austrobesa, 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 : 88-89

Hydraena austrobesa , new species

( Figs. 150 , 152, 502 )

Type Material. Holotype (male): Central Province: nr. Port Moresby, Sogeri Plateau, Musgrave River , under wet moss on rocky seepage, [GE est.] 100–200 m, 9° 46' S, 147° 41' E, 16 iii 1965, M. E. Bacchus (MEB 201) ( NHM) . Paratypes: Same data as holotype (20 NHM) .

Differential Diagnosis. Similar to H. limbobesa in body proportions and the coarse and dense dorsal punctation ( Figs. 150 , 151 ); differing therefrom by the pronotal sides emarginate between the anterior angle and the widest part, the more evident microreticulation of the head and pronotum, and the slightly larger size (ca. 1.43 vs. 1.36 mm). The metaventral plaques are quite similar in the two species. The male genitalia of the two species differ distinctively; reliable determinations will require dissections ( Figs. 152, 153).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.44/0.61; head 0.23/0.36; pronotum 0.36/0.48, PA 0.38, PB 0.43; elytra 0.86/0.61. Dorsum dark brown, head and pronotal disc piceous; legs brown; maxillary palpi light brown, tip not darker.

Frons punctures ca. 1xef, slightly larger and denser near eyes than medially; interstices microreticulate and dull laterally, effacedly microreticulate and very weakly shining medially, 1–2xpd. Clypeus microreticulate laterally, finely, sparsely punctate medially. Mentum dull, effacedly microreticulate and very sparsely very finely punctulate, postmentum microreticulate medially, finely punctate and shining anteriorly and laterally. Genae raised, shining, without posterior ridge. Pronotum moderately transverse (PL/PW ca. 0.75), ca. median 3/5 of anterior margin very slightly emarginate; sides slightly emarginate between anterior angle and widest part; coarsely, densely punctate, punctures on disc much deeper and ca. 3–4xpd frons punctures, interstices on disc effacedly microreticulate, weakly shining, narrow walls to 1xpd, interstices microreticulate and dull in impressions, punctures denser at anterior and posterior; PF1 shallow, obsolete; PF2 shallow; PF3 deep; PF4 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, a few punctures subserial, punctures becoming gradually smaller toward posterior. Intervals not raised, weakly shining, on disc ca. 1xpd, 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. 2/1/5/4. P1 laminate; median carina sinuate in profile. P2 narrow, raised slightly, l/w ca. 3/1, sides slightly diverging toward apex. Rim of mesocoxal cavity produced as very short carina on metaventrite. Plaques very narrow, weakly raised, converging slightly anteriorly, at sides of median depression that does not continue to P2. Metaventrite without midlongitudinal ridge. AIS width at straight posterior margin ca. 2xP2. All legs rather short, femora moderately robust. Profemur (male) without tubercle next to trochanter; protibia widest at about distal 1/3, medial margin very slightly emarginate, lateral margin weakly arcuate. Mesotibia straight, lateral margin slightly arcuate and bearing contiguous row of short stout spines. Metatibia straight, very slightly widened, widest at about distal 1/3. Abdominal apex symmetrical; last tergite (male) notched. Aedeagus as illustrated ( Fig. 152).

Etymology. Named in reference to its geographic distribution in the South Papuan Peninsula Foreland (Area 11), and its placement in the Spinobesa group.

Distribution. Currently known only from the type locality, the Musgrave River, in central Area 11; elevation 100–200 m ( Fig. 502 ).

Figures

FIGURE 150. Hydraena austrobesa, holotype, dorsal and lateral habitus, and venter.

FIGURE 151. Hydraena limbobesa, holotype, dorsal and lateral habitus, and venter.

FIGURES 499–502. Geographical distributions of Hydraena species.