Hydraena carinocisiva, 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 : 130

Hydraena carinocisiva , new species

( Figs. 239 , 241, 541 )

Type Material. Holotype (male): Eastern Highlands Province: Aiyura , creek, 1670 m, 6° 21.131' S, 145° 54.398' E, 20 v 2006, John & Balke ( PNG 70) ( ZSM) . Paratypes: Same data as holotype (4 ZSM) .

Differential Diagnosis. Differing from the other members of the Incisiva group by the carinate metaventral plaques (plaque ratios ca. 5/1.5/7/5); otherwise very similar ( Figs. 234 , 235 , 238 , 239 ). The aedeagus is very distinctive and should be examined for reliable determinations ( Fig. 241).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.66/0.68; head 0.25/0.36; pronotum 0.41/0.53, PA 0.40, PB 0.52; elytra 1.01/0.68. Dorsum of head with frons dark reddish brown, clypeus brown, labrum testaceous; pronotum testaceous around very faint, diffusely margined, light brown rectangular macula, color bands grading into one another on slightly teneral holotype, color band ratios ca. 8/10/7 on less teneral paratype; elytra dark brown; legs light brown; maxillary palpi testaceous, tip not darker. Dorsum shiny.

Frons punctures ca. 1xef near eyes, smaller and sparser medially; interstices shining, 1–2xpd laterally, ca. 2– 5xpd medially. Clypeus effacedly microreticulate laterally, very finely sparsely punctulate medially. Mentum and postmentum very sparsely very finely punctulate, shining. Genae very slightly raised, shining, without posterior ridge. Pronotum subtrapezoidal, ca. median 3/4 of anterior margin slightly arcuate to posterior, sides arcuate, slightly emarginate between midlength and posterior angle; punctures on disc slightly smaller than largest frons punctures, interstices strongly shining, ca. 2–4xpd, punctures anteriorly and posteriorly slightly larger than those on disc; PF1, PF2 and PF4 absent; PF3 moderately deep.

Elytra with posterior declivity very gradual, summit 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. 2–4xpd, 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. 5/1.5/7/5. P1 laminate; median carina nearly straight in profile, very slightly arcuate between coxae. P2 transversely concave, length ca. equal width, sides parallel or very slightly converging toward blunt apex. Plaques flat anteriorly, becoming gradually weakly raised to form low carina posteriorly, very slightly converging anteriorly, almost parallel, at sides of median depression. Metaventrite flat between mesocoxae. AIS width at straight posterior margin slightly greater than P2. All legs of moderate length. Profemur (male) with very small tubercle next to trochanter; protibia straight, medial margin increasing in width from base to distal 1/4, then excavate to apex, few large spines at base of excavation, and contiguous row of very short spines along excavation. Mesotibia straight, slender. Metatibia straight, slender, widest at midlength. Abdominal apex symmetrical, distinctly microreticulate; last tergite (male) with small apicomedian notch. Aedeagus as illustrated ( Fig. 241).

Etymology. This is the only species in the Incisiva group with carinate plaques.

Distribution. Currently known only from the type locality, Aiyura, in the far eastern part of Area 1, at the bor- der with Area 2; elevation 1670 m ( Fig. 541 ).

Figures

FIGURE 234. Hydraena incisiva, holotype, dorsal and lateral habitus, and venter.

FIGURE 235. Hydraena picula, holotype, dorsal and lateral habitus, and venter.

FIGURE 238. Hydraena carmellita, holotype, dorsal and lateral habitus, and venter.

FIGURE 239. Hydraena carinocisiva, holotype, dorsal and lateral habitus, and venter.

FIGURES 539–542. Geographical distributions of Hydraena species.