Pala

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 : 113

Pala group

Ten species are included in the Pala group: H. pala , H. maculopala , H. nanopala , H. palamita , H. formosopala , H. tritropis , H. torosopala , H. koje , H. dudgeoni , and H. fasciolata ( Figs. 202 , 203 , 206 , 207 , 210 , 211 , 214 , 215 , 218 , 219 ). Members of this group are very small to moderately sized (ca. 1.23 to 1.58 mm), with distinctive coloration, and a broad body shape. Species in this group (except H. tritropis ) are unique in the shape of the prosternal intercoxal process: it is relatively wide, the midlongitudinal carina is restricted to the anterior part of the prosternum, and the intercoxal part is wide and concave (e.g., Figs. 214 , 219 ). The color varies somewhat, but the pronotum usually does not have a fascia or macula, is usually light brown or testaceous, lighter than the frons and the elytra. In a few species the elytra are fasciate.

Some of the broadest species of PNG Hydraena are found in this group. The mesoventral intercoxal process (P2) is comparatively wide and concave, and all of the species have widely separated, carinate plaques. The protibiae of males are modified, but not markedly so. The male genitalia have a similar basic plan, with a tendency for the left paramere to be rotated toward the dorsal surface of the aedeagus (e.g. Figs. 220, 221 ).

Members of the Pala group are similar to members of the Impala group, but the latter have the midlongitudinal carina of the prosternum extending the entire length; therefore the posterior part is not concave. Although H. tritropis lacks the concave prosternal intercoxal area, the carina is straight, not bisinuate as in members of the Impala group; the form of the aedeagus of this species also supports its placement in the Pala group. The female tergite X, gonocoxite, and spermatheca of H. pala are illustrated ( Fig. 411 ); as expected, they show some similarities (setal patterns, spermatheca shape) with those structures in the Impala group, but have a very differently shaped tergite X ( Figs. 410, 411 ).

Members of the Pala group have only been collected in lowland rain forest, at an elevation range of 160–400 m (maps Figs. 428 , 527–533 ). Only the three following microhabitat descriptors are given in the locality records: "ex. gravel banks"; "unshaded creek, small to medium cobbles, gravel and fine sand (the latter in areas of slack water), filamentous algae on stony substrates, small accumulations of leaf litter"; "river."

Five species in the Pala group were collected from Kojé Creek in Area 3. In fact, four species in the group are only known from that site ( Fig. 528 ). These collections were made during a large rotenone study ( Dudgeon 1990, 1994). A total of 13 species of Hydraena were collected, and the site is the type locality of seven species, six of which are only known from there. Probably because of the collection method, via rotenone, the specimens were not well preserved and most of them lack some or all of the legs, or parts of legs, and maxillary palpi. The species in the Pala group from Koje are quite difficult, and require dissection of males for reliable determinations. Because of this decomposed condition, many females (ca. 300) from the Koje site were not identified.

Figures

FIGURE 202. Hydraena pala, holotype, dorsal and lateral habitus, and venter.

FIGURE 203. Hydraena maculopala, holotype, dorsal and lateral habitus, and venter.

FIGURE 206. Hydraena nanopala, holotype, dorsal and lateral habitus, and venter.

FIGURE 207. Hydraena palamita, holotype, dorsal and lateral habitus, and venter.

FIGURE 210. Hydraena formosopala, holotype, dorsal and lateral habitus, and venter.

FIGURE 211. Hydraena tritropis, holotype, dorsal and lateral habitus, and venter.

FIGURE 214. Hydraena torosopala, holotype, dorsal and lateral habitus, and venter.

FIGURE 215. Hydraena koje, holotype, dorsal and lateral habitus, and venter.

FIGURE 218. Hydraena dudgeoni, holotype, dorsal and lateral habitus, and venter.

FIGURE 219. Hydraena fasciolata, holotype, dorsal and lateral habitus, and venter.

FIGURES 220–221. Aedeagi of holotypes. 220. H. dudgeoni. 221. H. fasciolata.

FIGURES 408–411. Female tergite X, gonocoxite, and spermatheca of Hydraena species.

FIGURES 427–428. 427. Collecting sites for the nine members of the impala species group, all in montane rain forest. 428. Collecting sites for the ten members of the pala species group, all in lowland rain forest.

FIGURES 527–530. Geographical distributions of Hydraena species.

FIGURES 531–534. Geographical distributions of Hydraena species.