Hydraena ulna, 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 : 121-122

Hydraena ulna , new species

( Figs. 222 , 224, 412 , 537 )

Type Material. Holotype (male): Morobe Province: Herzog Mts., Vagau [Wagau], ex shallow pools in marsh, 1128 m, 6° 48' S, 146° 48' E, 8 i 1965, M. E. Bacchus (MEB 144) ( NHM) . Paratypes (13): Morobe Province: Same data as holotype (3 NHM); Herzog Mts., Vagau [Wagau], ex gravel banks of swift shallow clear river, 1128 m, 6° 48' S, 146° 48' E, 8 i 1965, M. E. Bacchus (MEB 145a) (10 NHM) .

Differential Diagnosis. Similar in dorsal habitus and plaque ratios to H. pectenata ( Figs. 222 , 223 ); differing therefrom in slightly larger size (ca. 1.57 vs. 1.46 mm), less densely punctate pronotum (discal interstices ca. 2–4 vs. 1–2 xpd). The male genitalia of the two species also show a relationship, while differing distinctively in several details ( Figs. 224, 225).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.57/0.69; head 0.21/0.36; pronotum 0.40/0.53, PA 0.41, PB 0.48; elytra 0.97/0.69. Dorsum of head dark brown to piceous; pronotum dark brown around piceous, very diffusely margined, rectangular macula, ratios of color bands, as measured in midline, ca. 8/15/5; elytra dark brown; legs brown; maxillary palpi testaceous, tip not darker. Dorsum moderately shining.

Frons punctures ca. 2xef near eyes, smaller and sparser medially; interstices shining, 1–4xpd. Clypeus effacedly microreticulate laterally, very finely sparsely punctulate and shining medially. Mentum effacedly microreticulate, very sparsely very finely punctulate, weakly shining. Postmentum microreticulate in shallow median depression, otherwise finely sparsely punctate. Genae very slightly raised, shining, with shallow, obsolete median impression, without posterior ridge. Pronotum transverse, anterior margin straight, sides straight between anterior angle and widest part, arcuate at middle, sinuate between widest part and slightly outward turning posterior angle; punctures on disc ca. 2xpd largest frons punctures, interstices shining, ca. 2–4xpd, punctures anteriorly and posteriorly ca. 2xpd those on disc; PF1, PF2 and PF4 very shallow; PF3 moderately deep, wide.

Elytra widest at about midlength; summit of posterior declivity at or very near midlength; lateral explanate margins moderately wide; on basal 1/3 punctures slightly smaller than 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. 3/2/8/4. P1 laminate; median carina sinuate in profile, slightly raised between coxae. P2 length/width ca. 5/3, sides very slightly converging toward blunt, slightly raised apex. Plaques flat, at sloping sides of median depression, anteriorly tapering and convergent, narrowly separated at anterior extreme. Metaventrite between mesocoxae very weakly raised in midline. AIS width at straight posterior margin ca. 1.5x P2. All legs of moderate length. Profemur (male) without tubercle on ventral margin; protibia straight, medial margin slightly emarginate over middle 1/3, then widened in distal 1/3, greatest width ca. twice width at midlength. Meso- and metatibia straight, slender. Abdominal apex very slightly asymmetrical; last tergite (male) with very small apicomedian notch. Aedeagus as illustrated ( Fig. 224). Female tergite X, gonocoxite, and spermatheca as illustrated ( Fig. 412 ).

Etymology. Named in reference to the elbow-shaped process of the aedeagus.

Distribution. Currently known only from the type locality, Wagau, in the Herzog Mts. (Area 6), elevation 1128 m ( Fig. 537 ).

Figures

FIGURE 222. Hydraena ulna, holotype, dorsal and lateral habitus, and venter.

FIGURE 223. Hydraena pectenata, holotype, dorsal and lateral habitus, and venter.

FIGURES 412–415. Female tergite X, gonocoxite, and spermatheca of Hydraena species.

FIGURES 535–538. Geographical distributions of Hydraena species.