Ulna, Capuse, 1973

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 : 121

Ulna group

Three species are included in the Ulna group: H. ulna , H. apexa , and H. pectenata ( Figs. 222 , 223 , 226 ). Members of this group are moderately sized (ca. 1.46 to 1.57 mm), darkly colored species with a rather obscure piceous pronotal macula or fascia that is bordered by dark brown. The pronotum is coarsely punctate and rather distinctively shaped, the anterior margin is straight and not as wide as the posterior margin; PF1 and PF2 are present, but shallow. The metaventral plaques are quite similar in the three species: widely spaced basally, arcuate, converging and very narrowly separated anteriorly. P1 is laminate and P2 is only slightly wider than plaque width, not concave, and with tip slightly raised.

Males of one species, H. apexa , have distinctively arcuate metatibiae. The male genitalia in this group have a diagnositic combination of characters: the distal piece has a very large process on the right side, the parameres are long and narrow, and the dorsal surface has a cluster of setae on each side, at the juncture of the main piece and distal piece ( Figs. 224, 225, 228). The female tergite X, gonocoxite, and spermatheca of H. ulna and H. pectenata are illustrated ( Figs. 412, 413 ); these differ slightly in proportions, but both have tergite X with three incisions, delimiting four lobes.

Members of the Ulna group have been collected at an elevation range of 1067–1670 m (maps Figs. 535–537 ). As is currently known, Areas 1, 5, and 6 each have an endemic species. Available microhabitat data mostly indicate pool biotopes: under wet leaves left by receding pond; small pool, probably permanent, in clay in dense shade; gravel banks of swift shallow clear river; shallow pools in marsh.

Figures

FIGURE 222. Hydraena ulna, holotype, dorsal and lateral habitus, and venter.

FIGURE 223. Hydraena pectenata, holotype, dorsal and lateral habitus, and venter.

FIGURE 226. Hydraena apexa, holotype, dorsal and lateral habitus, and venter.

FIGURES 412–415. Female tergite X, gonocoxite, and spermatheca of Hydraena species.

FIGURES 535–538. Geographical distributions of Hydraena species.