Hydraena picula, 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 : 128-129

Hydraena picula , new species

( Figs. 235 , 237, 540 )

Type Material. Holotype (male): Eastern Highlands Province: Goroka , Daulo Pass, 2500 m, 6° 2.432' S, 145° 13.333' E, 19 v 2006, John & Balke ( PNG 67) ( ZSM) . Paratypes (12): Eastern Highlands Province: Akameku– Brahmin, Bismarck Range, 2200 m, 5° 56.801' S, 145° 22.238' E, 23 xi 2006, Balke & Kinibel ( PNG 106) (1 ZSM) ; Akameku–Brahmin, Bismarck Range, 1900 m, 5° 54.284' S, 144° 22.271' E, 23 xi 2006, Balke & Kinibel ( PNG 108) (5 ZSM) ; Goroka, Daulo Pass, 2500 m, 6° 2.432' S, 145° 13.333' E, 19 v 2006, John & Balke ( PNG 67) (6 MCZ, NHM, NMW, PNG, ZSM) .

Differential Diagnosis. Differing from the other maculate members of the Incisiva group by the larger size (ca. 1.84 vs. 1.58–1.66 mm); otherwise very similar ( Fig. 235 ). The aedeagus is very distinctive and should be examined for reliable determinations ( Fig. 237).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.84/0.78; head 0.26/0.42; pronotum 0.45/0.61, PA 0.45, PB 0.58; elytra 1.14/0.78. Dorsum of head with frons dark reddish brown, clypeus brown, labrum testaceous; pronotum testaceous around light brown rectangular macula, ratios of color bands, as measured in midline, ca. 9/15/7; elytra dark brown; legs light brown; maxillary palpi light brown to testaceous, tip not darker. Dorsum shiny.

Frons punctures ca. 1–2xef near eyes, smaller and sparser medially; interstices shining, 1–2xpd laterally, ca. 1– 3xpd medially. Clypeus effacedly microreticulate laterally, very finely sparsely punctulate medially. Mentum very sparsely very finely punctulate, shining. Postmentum effacedly microreticulate, and finely punctulate, weakly shining. Genae very slightly raised except with shallow impression in midline, 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 smaller than largest frons punctures, interstices strongly shining, ca. 2–6xpd, punctures 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 slightly smaller than largest pronotal punctures, a few punctures subserial, 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. 5/2/8/6. P1 laminate; median carina nearly straight in profile, very slightly arcuate between coxae. P2 transversely concave, length slightly greater than width, sides parallel, apex blunt. Plaques roundly slightly raised, tapering anteriorly, very slightly converging anteriorly, almost parallel, at sides of median depression. Metaventrite flat between mesocoxae. AIS width at straight posterior margin ca. 1.5x P2. All legs of moderate length, tibiae slender. Profemur (male) without 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. Meso- and Metatibia straight, very slen- der. Abdominal apex symmetrical; last tergite (male) with small apicomedian notch. Aedeagus as illustrated ( Fig. 237).

Etymology. "Little woodpecker"; named in reference to the shape of the aedeagus.

Distribution. Currently known from three localities in eastern Area 1, at the relatively high elevations of 1900 m, 2200 m, and 2500 m ( Fig. 540 ).

Figures

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

FIGURES 539–542. Geographical distributions of Hydraena species.