Gymnochthebius papua, Perkins, 2005

Perkins, Philip D., 2005, A revision of the water beetle genus Gymnochthebius Orchymont (Coleoptera: Hydraenidae) for Australia and Papua New Guinea, Zootaxa 1024 (1), pp. 1-161 : 1-161

Gymnochthebius papua new species

(Figures 70, 71)

Type Material. Holotype (male): Papua New Guinea: Morobe District, ca. 10 km S Garaina Saureri , elev. 1600 m, 24 March 1998, leg. A. Riedel. Deposited in the NMW . Paratypes: same data as holotype (23 NMW). Representative specimens to be deposited in ANIC, MCZ, NPC, QMBA and SAMA .

Differential Diagnosis. A very distinctive species, recognized by the impunctate head and pronotum contrasting with the deeply punctate elytra, the small apicomedian process of the anterior pronotal margin, the deep pronotal foveae, the wide lateral pronotal depressions, and the diamond­shaped anterior part of the median groove. Markedly differing from G. bacchusi , the other species known from Papua New Guinea, in body form, pronotal form and sculpture, and aedeagus (Figs. 33, 34, 70, 71).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.58/ 0.74; head 0.31/0.43; pronotum 0.38/0.63; elytra 0.94/0.74. Form moderately ovate, pronotum transverse, elytra strongly convex. Color brown, head darker, dorsal reliefs weakly shining.

Head impunctate dorsally, with short sparse setae, each setal base minutely raised. Frons interocular foveae deep; interocular tuberculi distinct; basal foveae confluent with interocular foveae, medially separated by carina. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength 0.5 apical width. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum width 2x length; anterior margin arcuate, setose, without apicomedian tooth. Maxillary palpomere 3 slightly greater than twice length of 4.

Pronotum anterior hyaline border well developed, widest in front of lateral fossulae; lateral hyaline border well developed, origin at base of lateral depression, arcuate to posterior angles, very narrow around posterior margin; anterior margin of pronotum produced in small point medially, margin straight and angles slightly posteriorly on each side of point, arcuate at anterior angles; lateral depression wide, each with posterior angle acute point, lateral margin arcuate, with short fringe of setae; lateral fossulae deep, lacking microsculpture, anteriorly with small pit­like fovea bearing minute point on anterior and posterior margins; pronotal disc transversely moderately convex, impunctate, with short sparse setae, most setae with socket minutely raised; median groove deep, wide, extending nearly to margins, tapering at ends, constricted near midlength, anterior part diamond shaped and slightly wider than posterior part; anterior foveae oval, relatively large and deep; posterior foveae deep, elongate, similar in size to posterior part of median groove; posterolateral angles without impressions.

Elytra very convex on disc, with six rows of moderately large, deep punctures between suture and humeri, not striate­impressed; punctures each with a distinctive decumbent seta; intervals weakly rounded, if at all, width equal that of punctures; declivity steep, summit near midlength, where elytra are transversely markedly convex; sutural margin slightly raised over posterior declivity; explanate margin moderately narrow, decumbent setae on margin forming very narrow fringe.

Metasternal glabrous area circular or nearly so, convex, shining. Short midlongitudinal carina from intercoxal process to glabrous area. Abdominal ventrites 1–3 and anteriorly 4 with hydrofuge pubescence.

Aedeagus (Fig. 71): Length of main­piece 0.27 mm, length to tip of parameres 0.32 mm; lobes long and distinctively barbed; parameres extending well beyond tips of lobes, slightly widened on medial surface, apical seta only slightly longer than subapical setae.

Female last tergite with apical fringe of short, flat, stout, contiguous setae.

Etymology. Named in reference to the geographical distribution.

Distribution. Currently known from Papua New Guinea.

Notes. The type series was heavily coated with debris. During the process of removing the debris from the holotype, some setae on the head and pronotum were unavoidably abraded. The former locations of the setae are indicated by the minutely raised rim of each setal socket (Fig. 70).