Gymnochthebius brisbanensis (Blackburn) 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 brisbanensis (Blackburn) new combination

(Figures 35, 36, 79)

Ochthebius brisbanensis Blackburn 1898: 229 .

Type Material. Holotype (by monotypy; female): Australia: Queensland: Brisbane, Kedron Pk., [labels: "TYPE [red disc]"; "”6373” Qu. [red] T."; " Kedron Pk., Brisbane. C. Wild, 1892"; " Blackburn coll. 1910­236"; " Ochthebius brisbanensis, Blackb. "]. Deposited in the BMNH.

Differential Diagnosis. Recognized by the dull, matte dorsum, the abdominal ventrites 1–3 and minutely anteriorly 4 with hydrofuge pubescence, and the arcuate labrum in both sexes. Distinguished from G. levis , which also has a dull, pruinose dorsum, by the larger size, the more convex form, the more extensive hydrofuge pubescence, the lack of an apicomedian process of the labrum in males, and the male genitalia. Distinguished from G. fumosus by the finely sparsely punctate pronotal reliefs, the smaller elytral serial punctures, and the shining metasternal glabrous area. The male genitalia show some resemblance to that of G. fumosus , but in G. brisbanensis the lobes are shorter and more strongly barbed, the duct markedly arcuate, and the parameres extend further beyond the main­piece (Figs. 36, 38).

Description. Size (length/width, mm) holotype: body (length to elytral apices): 1.73/ 0.73; head 0.31/0.44; pronotum 0.41/0.64; elytra 1.07/0.73. Form moderately ovate, moderately convex. Color dark brown, entire dorsal surface dull.

Frons very finely sparsely punctate, nearly impunctate, very sparsely pubescent; interocular foveae deep; interocular tuberculi distinct; basomedial depression with very weak midlongitudinal carina, depression anteriorly narrowly confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength 0.5x apical width, very sparsely punctate; pubescence very sparse on disc, slightly denser laterally. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum width twice length, anterior margin arcuate.

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 slightly produced in midregion; each lateral depression with posterior angle produced as acute point, lateral margin arcuate, with distinct fringe of short arcuate setae; lateral fossulae deep, microsculpture similar to remainder of pronotum; pronotal disc moderately convex, extremely finely sparsely punctate, setae very small and fine, if perceptible; median groove shallow, very narrow, extending nearly to margins, tapering at ends; anterior foveae small, pit­like at bottom of depression; posterior foveae oblique, linear impressions nearly 1/2 as long as and subequal width of median groove; posterolateral angles each with shallow impression.

Elytra moderately convex on disc, with six rows of small punctures between suture and humeri; punctures round, separated from each other by about puncture width, each with very fine seta; intervals rounded, width twice that of punctures; sutural interval raised; summit of declivity slightly behind midlength; striae 2 and 3 terminating into 4 at about apical 0.2; elytral margin lacking prominent setae.

Prosternum with weak midlongitudinal carina. Metasternal glabrous area large, shining, convex, oval, slightly longer than wide (as 6:5). Abdominal ventrites 1–3 and minutely anteriorly 4 with hydrofuge pubescence.

Aedeagus (Fig. 36): Length of main­piece 0.27 mm, length to tip of parameres 0.29 mm; lobes relatively long, strongly barbed; notches U­shaped, ventral notch slightly narrowed apically, dorsal notch slightly wider than ventral notch; duct markedly arcuate at base of notches, then gradually enlarged to rounded apex; apical paramere seta elongate and sinuate, ca. 2–3x length of next longest seta.

Females have the explanate elytral margin and the labrum similar to that of males.

Distribution. A rarely collected species, currently known from Brisbane south to southwestern Victoria (Fig. 79).

Notes. Specimens from Victoria generally have the elytral setae slightly more apparent than specimens from more northern localities. The single male from Grampians National Park is smaller than usual, and the male genitalia differ very slightly from other specimens.

Material Examined (43): Australia: New South Wales: Cattai Creek NW of Sydney, creek, 33° 42' S, 150° 59' E, 12 December 1988, V. Lorimer (1 AMSA) ; [no other data], 1 January–30 December 1858, Griffith (24 SAMA) ; Sydney [no date], 33° 52' S, 151° 12' E, Lea (2 SAMA) ; Tamworth [no date], 31° 5' S, 150° 55' E, Lea (3 SAMA) ; Victoria: 10 km NE Mirranatwa , small creek bed ­ drying pool, stony, dead leaves, dry sclerophyll forest, 37° 36' S, 142° 13' E, 12 October 1997, C. Watts (8 SAMA) ; Burrong Falls, 6.0 km W Mt. Victory, Grampians N.P., ex. margins of vertical and horizontal rockfaces (sandstone) of waterfalls. Dry sclerophyll forest, elev. 280 m, 37° 9' S, 142° 23' E, 2 March 1999, N. Porch (NP 42) (1 ANIC) ; Cann River , flood debris, 37° 29' S, 149° 9' E, 20–25 May 1978, S. & J. Peck (3 ANIC) . Representative specimens to be deposited in MCZ, NPC, and QMBA .