Gymnochthebius benesculptus, 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 benesculptus new species

(Figures 42, 43, 91)

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 (30): Australia: South Australia: Salt Ck at Mangalo , 33° 32' S, 136° 37' E, 10 November 1994, Aust. water quality centre 3686 (5 SAMA) ; Stoney Crossing, 8 km SW Kalamurina HS, Warburton River , 27° 46' S, 138° 12' E, 7 October 1999, WHC exped. (1 SAMA) ; Warburton R., 1 km N White Bull Yard Kalamurina Stn., 27° 52' S, 137° 54' E, 6 October 1999, WHC exped. (20 SAMA) ; Willochra Ck. , 2 km E “Proby’s Grave”, 34° 4' S, 138° 6' E, 8 May 1981, J. A. Forrest (4 SAMA) . Representative specimens to be deposited in ANIC, MCZ, NMW, NPC, and QMBA.

Differential Diagnosis. Recognized by elongate body form and elongate legs, the comparatively large elytra, the large and deep pronotal foveae, the shining dorsal reliefs, the deeply striate­impressed elytral series, and the equally wide and convex elytral intervals. Distinguished from G. coruscus and G.weiri by the very uniform height of the elytral intervals, the darker body coloration, and subtle differences in body proportions (Figs. 42, 44, 46). The male genitalia are most similar to that of G. sexplanatus , but differ in shape of the main­piece and paramere setae (Figs. 43, 49).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 2.00/ 0.82; head 0.37/0.46; pronotum 0.44/0.59; elytra 1.30/0.82. Form moderately ovate, moderately convex. Dorsum brown to dark brown, head dark brown to black; dorsal reliefs strongly shining.

Head dorsally 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, slightly more developed laterally. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum length 0.5 width, anterior margin strongly arcuate; apicomedian tooth very low, behind which is oval depression. Maxillary palpomere 3 slightly greater than twice length of 4.

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 slightly produced in midregion; each lateral depression wide, posterior angle produced to acute point, lateral margin arcuate, with very short fringe of setae; lateral fossulae deep, non­microreticulate; pronotal disc 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, wider than 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 with indistinct shallow 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 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 16:12), oval, shining, convex. Abdominal ventrites 1–3 and basal part of 4 with hydrofuge pubescence.

Aedeagus (Fig. 43): Length of main­piece 0.38 mm, length to tip of parameres 0.43 mm; lobes relatively long, strongly barbed; dorsal notch U­shaped, wider than V­shaped ventral notch; apical paramere seta elongate, subapical seta ca. 0.5x as long.

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 reference to the markedly sculptured pronotum and elytra.

Distribution. Currently known from central and south­central South Australia (Fig. 91).