Gymnochthebius coruscus, 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 coruscus new species

(Figures 44, 45, 89)

Type Material. Holotype (male): Australia: South Australia: Warburton R., 1 km N White Bull Yard Kalamurina Stn. , 27° 52' S, 137° 54' E, 6 October 1999, WHC exped. Deposited in the SAMA . Paratypes: Same data as holotype (7 SAMA). Representative specimens to be deposited in MCZ and NPC .

Differential Diagnosis. Recognized by the black head and bright testaceous pronotum and elytra, the elongate body form and legs, the large and deep pronotal foveae, the shining dorsal reliefs, and the deeply striate­impressed elytral series. Distinguished from G. benesculptus by the slightly more ovate body form, the less raised elytral intervals beyond the posterior declivity, and the lighter coloration (Figs. 42, 44). Distinguished from G. sexplanatus by the more strongly striate­impressed elytral series and relatively smaller pronotum (Fig. 48). The male genitalia distinctly differ from that of both compared species, being weakly barbed and with each paramere bearing a pair of thickened, elongate setae (Figs. 43, 45, 49).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 2.15/ 0.94; head 0.39/0.52; pronotum 0.48/0.69; elytra 1.41/0.94. Form moderately ovate. Head black, pronotum, elytra and appendages testaceous or light brown, dorsal reliefs shiny, non­microreticulate.

Head shiny, frons finely sparsely punctate, sparsely pubescent; interocular foveae shallow; interocular tuberculi distinct; basomedial fovea confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus parallel­sided, midlength:apical width 4:7, finely, moderately densely punctate; pubescence very sparse on disc, slightly more developed laterally. Labroclypeal suture weakly concave in dorsal view, evenly arcuate in anterior view. Labrum length:width 3:7, anterior margin arcuate, with prominent apicomedian upturned tooth, behind which is oval depression.

Pronotum lateral hyaline border well developed, origin at base of lateral depression, margin nearly straight, then markedly arcuate to posterior angles, very narrow around posterior margin; anterior margin of pronotum slightly arcuate in midregion; each lateral depression wide, weakly arcuate from anterior angles, then emarginate before acute posterior angle, lateral margin with fringe of very short setae; lateral fossulae deep, surface irregular; pronotal disc weakly convex, reliefs shiny, finely sparsely punctate, each puncture with minute recumbent seta; median groove deep, narrow, constricted in midlength, extending nearly to margins, tapering at ends; anterior foveae oval, deep, 2–3x greatest width of median groove; posterior foveae oval, oblique, deep, 0.5 as long as and 2–3x as wide as median groove; posterolateral angles lacking 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; intervals high, rounded, very uniform, 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 not continuing in raised condition to apices; sutural margin not raised; elytral explanate margin moderately developed, without fringe of setae.

Metasternal glabrous area longer than wide (as 17:12), widest behind midlength, flat or weakly convex. Abdominal ventrites 1–3 and basally 4 with hydrofuge pubescence.

Aedeagus (Fig. 45): Length of main­piece 0.39 mm, length to tip of parameres 0.45 mm; lobes relatively long, weakly barbed at apex; apical two paramere setae elongate, thickened, joined together, much longer than other setae.

Females have the explanate elytral margin markedly arcuate, about twice as wide as it is in males, slightly wider than the mesotibia; the anterior margin of the labrum is arcuate, lacking the apicomedian tooth found in males.

Etymology. Named in reference to the gleaming dorsum.

Distribution. Currently known only from the type locality in north­central South Australia (Fig. 89).