Hydraena tibiopaca, 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 : 101-102

Hydraena tibiopaca , new species

( Figs. 175 , 177, 507 )

Type Material. Holotype (male): Morobe Province: ridge between Aseki–Menyamya , 2200 m, 7° 12' S, 146° 4' E, 12 iv 1998, A. Riedel ( NMW) . Paratypes (11): Eastern Highlands Province: Akameku–Brahmin, Bismarck Range , 2400 m, 5° 55.615' S, 145° 22.699' E, 23 xi 2006, Balke & Kinibel ( PNG 107) (3 ZSM) ; Morobe Province: Same data as holotype (7 NMW) ; Western Highlands Province: Sepik River Basin, Waré Creek , partially shaded montane stream with angular, moss–covered boulders, small waterfalls and pools, 2000 m, 5° 42' S, 144° 39' E, 1 vii–30 viii 1988, D. Dudgeon (1 NMW) .

Differential Diagnosis. Among members of the Cristatigena group, recognized by the combination of the confluent pronotal foveae PF2, the coarsely punctate pronotum, the sharply rounded elytral apices, and the comparatively narrow explanate elytral margin. Somewhat similar in dorsal habitus to H. tritutela ; differing therefrom by the effacedly micropunctulate ground sculpture of the head and pronotum, the confluent PF2 foveae, the much more finely granulate elytra, and, in males, the differently shaped hind tibiae ( Figs. 163 , 167 ). The aedeagus of H. tibiopaca differs distinctively from that of other members of the Cristatigena group ( Fig. 177).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.75/0.76; head 0.28/0.43; pronotum 0.41/0.57, PA 0.46, PB 0.47; elytra 1.07/0.76. Dorsum dark brown to piceous, palpi light brown, except distal 1/3 of last palpomere darker.

Dorsum of head and pronotum effacedly punctulate, dull in impressions, weakly shining on reliefs; punctures of frons disc ca. 1xef, on pronotal disc ca. 2xef, interstices ca. 1xpd or slightly larger; punctures of clypeus smaller than those of frons. Labrum apicomedially excised, lobes rounded, free margins weakly upturned. Last maxillary palpomere (male) with slightly sinuate lateral margin. Mentum sparsely punctate, dull; postmentum anterior 1/2 with punctation similar to mentum, posterior 1/2 densely micropunctulate. Genae raised, posterior ridge strong. Pronotum with anterior margin very weakly emarginate over middle 1/2; PF1 with median posterior extension, almost confluent with transverse fovea formed by confluent PF2; PF3 and PF4 very deep.

Elytra moderately shining, punctures small, ca. 1xpd of largest pronotal punctures, each with very short seta, some with very minute granule at base of seta on anterior margin of puncture, most punctures without perceptible granules at sides of punctures. Intervals not raised, width ca. 2–3xpd, interstices between punctures of a row ca. 1– 2xpd. Apices in dorsal aspect conjointly, rather sharply rounded, in posterior aspect margins forming minute angle with one another. Explanate margin moderately developed, slightly narrower than widest part of metatibia.

Ratios of P2 width and plaque shape (P2/w/l/s) ca. 4/1/7/6. P1 laminate; median carina sinuate in profile. P2 moderately narrow, l/w ca. 2/1, sides parallel, apex blunt. Plaques very narrow, posteriorly carinate, more widely separated posteriorly than anteriorly, not arcuate, 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. 2x P2. Protibia (male) in lateral view gradually slightly widened from base to apex, in ventral view medial surface notched subapically, few short stout spine-like setae at base of notch; mesotibia simple; metatibia slender in ventral view, in lateral view markedly widened in distal 1/3, widened area concave on medial surface, upper rim with brush of short setae. Abdominal apex symmetrical.

Aedeagus ( Fig. 177) long compared with other members of group, main piece with large distal lobe, in ventral aspect, arching from right side toward left side, apically produced as sharply rounded lobe on left side; left paramere as long as and apically about as wide as distal lobe, widest apically, with two small lobes, each with a cluster of setae; right paramere slightly longer than and subapically slightly narrower than distal lobe of main piece, widest at about distal 2/3, apex sharply rounded; distal piece with large lobe of characteristic shape.

Etymology. Named in reference to the modified hind tibiae of males, and the dull dorsal sculpture.

Distribution. Currently known from three localities in the eastern part of Area 1; elevation range 2000–2400 m ( Fig. 507 ).

Figures

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

FIGURE 167. Hydraena labropaca, holotype, dorsal and lateral habitus, and venter.

FIGURE 175. Hydraena tibiopaca, holotype, dorsal and lateral habitus, and venter.

FIGURES 507–510. Geographical distributions of Hydraena species.