Hydraena balkei, 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 : 97

Hydraena balkei , new species

( Figs. 166 , 168, 508 )

Type Material. Holotype (male): Eastern Highlands Province: Akameku–Brahmin , Bismarck Range, 1200 m, 5° 52.754' S, 145° 23.209' E, 24 xi 2006, Balke & Kinibel ( PNG 110) ( ZSM) . Paratype: Eastern Highlands Province: Akameku–Brahmin , Bismarck Range, 2400 m, 5° 55.615' S, 145° 22.699' E, 23 xi 2006, Balke & Kinibel ( PNG 107) (1 male ZSM) .

Differential Diagnosis. Similar in dorsal habitus to H. tritutela and H. bacchusi ; differing therefrom by the larger size (ca. 2.17 vs. 1.83 and 1.67 mm), the more coarsely and densely punctate head and pronotum, and the much larger, non-carinate plaques ( Figs. 162 , 163 , 166 ). The shapes of the male hind tibiae differ in the three species. The aedeagus of H. balkei , while being the most divergent of the Cristatigena group, has a right paramere shape that suggests relationship with the compared species ( Figs. 164, 165, 168).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 2.17/0.99; head 0.35/0.53; pronotum 0.51/0.68, PA 0.58, PB 0.58; elytra 1.33/0.99. Dorsum piceous, legs dark brown, palpi brown, except distal 1/2 of last palpomere slightly darker.

Dorsum of head and pronotum densely punctate, interstices shining; punctures of frons 1xef or slightly larger, interstices 0.5–1xpd, punctures of clypeus distinct, smaller than punctures of frons; pronotal punctures coarse and dense, 2–3xpd of frons punctures, interstices narrow walls to ca. 1xpd or slightly larger. Labrum apicomedially excised, lobes rounded, free margins upturned. Mentum sparsely punctate, effacedly microreticulate, moderately dull; postmentum anterior 1/2 with punctation similar to mentum, posterior 1/2 densely micropunctulate. Genae raised, posterior ridge strong. Pronotum with anterior margin weakly emarginate over middle 1/2; all pronotal foveae deep, PF1 shallowly confluent with PF3, PF2's shallowly confluent with one another in middle, PF3 and PF4 deeper than other foveae.

Elytra dull, punctures slightly larger than largest pronotal punctures, each puncture with minute seta and three granules, one at anterior margin and one on each side. Intervals not raised, width 1–2xpd, as are interstices between punctures of a row. Apices in dorsal aspect conjointly rounded, in posterior aspect margins not forming angle with one another. Explanate margin well developed, about as wide as widest part of metatibia.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 1/1/11/1.7. P1 laminate; median carina sinuate in profile. P2 moderately narrow, l/w ca. 2.5/1, sides parallel, apex blunt. Plaques wide, weakly raised, diverging slightly from anterior to posterior, located at lateral margins of deep, median depression. Metaventrite tumid lateral to plaques. No midlongitudinal carina between mesoventral intercoxal process and plaques. Hydrofuge pubescence dense. AIS flat, width at straight posterior margin ca. 1.5x P2. Protibia (male) gradually, moderately widening from base to apex, in dorsal view medial surface weakly emarginate in distal 1/2; mesotibia simple; metatibia in lateral view markedly widened in distal 1/2, medial surface of widened area flat or concave, bearing brush of short setae. Abdominal apex symmetrical.

Aedeagus ( Fig. 168) main piece slightly twisted clockwise compared with basal ring; left paramere moderately large, produced as lobe on ventral margin, setae in two clusters; right paramere long, widest in distal 1/2, apically rounded, in right lateral aspect markedly arcuate toward ventral surface, setae in two clusters; distal piece large, with characteristic shape.

Etymology. Named in honor of the collector, Michael Balke, who has added so much to the knowledge of PNG water beetles.

Distribution. Currently known from two very narrowly separated localities in northeastern Area 1; elevations 1200 m and 2400 m ( Fig. 508 ).

Figures

FIGURE 162. Hydraena bacchusi, holotype, dorsal and lateral habitus, and venter.

FIGURE 163. Hydraena tritutela, holotype, dorsal and lateral habitus, and venter.

FIGURE 166. Hydraena balkei, holotype, dorsal and lateral habitus, and venter.

FIGURES 507–510. Geographical distributions of Hydraena species.