Gymnochthebius weiri, 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 weiri new species

(Figures 46, 47, 74)

Type Material. Holotype (male): Australia: Northern Territory: Finke River xing, Stuart Highway , flowing river (temporary), sandy base, over­hanging vegetation, 24° 33' S, 133° 14' E, 4 March 1995, T. Weir. Deposited in the ANIC . Paratypes: Same data as holotype (2 ANIC) .

Differential Diagnosis. Recognized by elongate body form and legs, the comparatively large elytra, the large and deep pronotal foveae, the shining dorsal reliefs, the light brown to testaceous color, and the raised even­numbered elytral intervals which are distinctly higher than the odd­numbered intervals. Distinguished from similarly shaped species G. benesculptus and G. coruscus by the elytral sculpture, the smaller size (ca. 1.70 mm vs. 2.00 mm), and the non­barbed aedeagus (Figs. 46, 47).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.67/ 0.76; head 0.31/0.36; pronotum 0.39/0.53; elytra 1.03/0.76. Form moderately ovate, moderately convex. Head piceous, pronotum and elytra light brown to testaceous. Dorsal reliefs shining.

Head finely sparsely punctate, weakly pubescent; interocular foveae deep; interocular tuberculi distinct; basomedial fovea narrowly confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength 0.5 apical width, pubescence very sparse on disc, denser and longer laterally. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum length 0.5 width, anterior margin strongly arcuate; apicomedian tooth strong, behind which is weak oval depression.

Pronotum lateral hyaline border well developed, origin at base of lateral depression, margin straight then markedly arcuate to posterior angles, very narrow around posterior margin; anterior margin of pronotum weakly arcuate in midregion; each lateral depression wide, posterior angle produced to acute point, lateral margin arcuate, with very short fringe of setae; lateral fossulae deep, very effacedly if at all microreticulate; pronotal disc transversely weakly convex, finely sparsely punctate, each puncture with a very small recumbent seta; median groove wide and deep, markedly constricted slightly behind midlength, extending nearly to margins, tapering at ends; anterior foveae oval, deep and large, width about equal widest part of median groove; posterior foveae oblique, deep, slightly more than 1/2 as long as and as wide as median groove; posterolateral angles without impressions.

Elytra moderately convex on disc, with six rows of punctures in deep striae between suture and humeri; punctures round, usually separated from each other by less than puncture width, sometimes narrow walls; even­numbered intervals raised, distinctly higher than odd­numbered intervals, width slightly greater than that of punctures; summit of declivity near apical 0.66; striae 2 and 3 terminating into 4 at about apical 1/4; intervals 4 and 6 continuing in raised condition to apices; sutural margin slightly raised; elytral explanate margin moderately developed, without fringe of setae.

Metasternal glabrous area longer than wide (as 14:12), oval, shining, convex. Abdominal ventrites 1–3 and basal part of 4 with hydrofuge pubescence.

Aedeagus (Fig. 47): Length of main­piece 0.32 mm, length to tip of parameres 0.38 mm; lobes relatively wide, not barbed; notches U­shaped, narrowed slightly subapically; duct markedly arcuate subapically; apical paramere seta elongate, much longer than other setae.

Females have the explanate elytral margin about twice as wide as it is in males, about equal to the width of the mesotibia; the elytral sutural margins are sometimes weakly emarginate just before the apices, forming a narrow gap between the elytra; the labrum is simple, lacking the apicomedian tooth found in males.

Etymology. Named in honor of the collector, Tom Weir.

Distribution. Currently known only from the type locality in the Finke River Gorge National Park area of central Australia (Fig. 74).