Gymnochthebius subsulcatus, 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 subsulcatus new species

(Figures 54, 55, 86)

Type Material. Holotype (male): Australia: South Australia: Dalhousie Springs , damp litter near hot springs, FMHD #83­677, 26° 27' S, 135° 28' E, 30 May 1983, L. E. Watrous. Deposited in the ANIC . Paratypes: Same data as holotype (2 ANIC) .

Differential Diagnosis. Recognized by the piceous color, the pronotal lateral margin produced in an obtuse point slightly anterior to midlength, the pronotal disc densely moderately coarsely punctate, the elytral series subsulcately impressed, and the elytral explanate margin narrow, with a short fringe of setae. The elytra and the male genitalia distinctly differ from that of other species (Figs. 54, 55).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.89/ 0.78; head 0.33/0.48; pronotum 0.44/0.67; elytra 1.11/0.78. Form moderately ovate, moderately convex. Color piceous, palpi and tarsi lighter, dorsum moderately shining.

Frons reliefs moderately punctate, sparsely pubescent; interocular foveae deep, continuing to posterior margin of head; interocular tuberculi very small, circular, located midway between midline and margin of eye; posterior area behind interocular tuberculi depressed from side to side; frons depressions effacedly microreticulate; Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength 0.5 apical width, moderately coarsely and densely punctate, dull; pubescence very sparse on disc, more developed later­ ally. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum length:width as 5:13, anterior margin arcuate, with very low apicomedian upturned tooth, oval depression behind tooth. Maxillary palpomere 3 about four times length of 4.

Pronotum lateral hyaline border well developed, origin at base of lateral depression, arcuate to posterior angles, very narrow around posterior margin; anterior margin of pronotum nearly straight in midregion, shallowly emarginate behind eye; each lateral depression with posterior angle produced to acute point, lateral margin setose, distinctly produced to an obtuse point slightly anterior to midlength; lateral fossulae deep, effacedly microreticulate, as are other foveae; pronotal disc moderately convex, moderately coarsely punctate, each puncture with a recumbent yellow seta which contrasts with dark cuticle; median groove moderately deep, narrow, extending nearly to margins, tapering at ends; anterior foveae well developed; posterior foveae oblique, linear impressions 1/2 as long as and slightly wider than median groove; posterolateral angles without impressions.

Elytra moderately convex on disc, with six rows of punctures in well developed striae between suture and humeri; intervals slightly raised, subsulcate, width 1.5–3.0x that of punctures, each interval with unilinear row of short decumbent setae each of which attains base of following seta, punctures round, separated from each other by about puncture width; summit of declivity slightly behind midlength; striae 2 and 3 terminating into 4 at about apical 1/4; explanate margin narrow, with short fringe of setae about 0.5 length of pronotal fringe.

Metasternal glabrous area length equal width, oval, shining, convex. Abdominal ventrites 1–3 and laterally 4 with hydrofuge pubescence.

Aedeagus (Fig. 55): Length of main­piece 0.28 mm, length to tip of parameres 0.31 mm; lobes relatively long, tapering, each lobe with a small barb basally and slightly bent apically; notch U­shaped, nearly parallel­sided; duct with cuticular crease at apex; apical paramere seta elongate, much longer than other apical setae but subequal length of more proximal setae; main­piece widened near midlength.

Females have the elytral explanate margin slightly wider than that of males; the labrum has a transverse oval subapicomedian depression like that of males, but lacks an apicomedian tooth.

Etymology. Named in reference to the subsulcate elytra.

Distribution. Currently known only from the type locality, Dalhousie Springs in northern South Australia (Fig. 86).