Hydraena hornabrooki, 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 : 136

Hydraena hornabrooki , new species

( Figs. 251 , 253, 546 )

Type Material. Holotype (male): East Sepik Province: Sepik, main river, 20 m, 4° 12' S, 143° 36' E, 2 iii 1965, R. W. Hornabrook ( NMNZ).

Differential Diagnosis. Differentiated from other members of the Fundextra group by the condition of the carinate metaventral plaques, which diverge anteriorly; in other species of the group the plaques are either parallel or converge anteriorly ( Fig. 251 ). The male genitalia distinctively differ from those of other members of the group ( Fig. 253).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.31/0.50; head 0.18/0.33; pronotum 0.33/0.46, PA 0.38, PB 0.43; elytra 0.79/0.50. Dorsum of head dark brown; pronotum light brown around dark brown to piceous, diffusely margined, rectangular macula, ratios of color bands, as measured in midline, ca. 6/ 12/5; elytra brown; legs brown; maxillary palpi testaceous, tip not darker. Dorsum very weakly shining.

Frons punctures ca. 1–2xef, slightly smaller and sparser medially; interstices effacedly microreticulate, dull, 0.5–2xpd. Clypeus effacedly microreticulate, very finely sparsely punctulate medially. Mentum very sparsely very finely punctulate, shining. Postmentum effacedly microreticulate in shallow median depression, otherwise finely sparsely punctate. Genae very slightly raised, shining, with shallow, obsolete median impression, without posterior ridge. Pronotum transverse, ca. median 3/4 of anterior margin slightly arcuate to posterior, sides arcuate, slightly emarginate between midlength and posterior angle; punctures on disc larger and deeper than largest frons punctures, interstices strongly shining, ca. 2–4xpd, punctures anteriorly and posteriorly slightly larger than those on disc; PF1 and PF4 absent; PF2 very shallow, completely shallowly confluent in midline to form U-shaped impression; PF3 moderately deep, wide.

Elytra with posterior declivity very gradual, summit at or very near midlength; lateral explanate margins moderately wide; on basal 1/3 punctures ca. 1xpd of 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. 4/1/8/6. P1 very slightly wider than laminate; in profile, median carina nearly straight in front of coxae, behind coxae raised slightly, arcuate in profile. P2 markedly concave, length/width ca. 5/4, sides very slightly converging toward blunt apex. Plaques low carinate lines, diverging slightly anteriorly, at sides of densely punctate median depression. Metaventrite between mesocoxae slightly sloping, confluent with tip of P2. AIS width at straight posterior margin slightly greater than P2. All legs of moderate length. Profemur (male) without tubercle on ventral margin; protibia straight, ventral margin flat in distal 2/3. Mesotibia straight, slender. Metatibia straight, slender, medial margin emarginate in distal 3/4. Abdominal apex asymmetrical; last tergite (male) with deep concavity near apex, offset to left side. Aedeagus as illustrated ( Fig. 253).

Etymology. Named in honor of the collector, Richard W. Hornabrook.

Distribution. Currently known only from the type locality, Sepik, main river, in the western arm of Area 3; elevation 20 m ( Fig. 546 ).

Figures

FIGURE 251. Hydraena hornabrooki, holotype, dorsal and lateral habitus, and venter.

FIGURES 543–546. Geographical distributions of Hydraena species.