Gymnochthebius squamifer, 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 squamifer new species

(Figures 66, 67, 74)

Type Material. Holotype (male): Australia: Queensland: N.Q., 15 km NE Mareeba , MDPI intercept trap site No. 25, flight intercept trap, 16° 56' S, 145° 32' E, 20 December 1984 – 7 January 1985, Storey & Titmarsh. Deposited in the QMBA . Paratypes (10): Australia: Northern Territory: 30 km N of Wauchope , 20° 22' S, 134° 14' E, 13 October 1972, M. S. Upton (1 ANIC) ; Butterfly Gorge Nature Pk Douglas River , at light, 13° 45' S, 131° 34' E, 19 July 1994, T. Weir & A. Roach (1 ANIC) ; Queensland: 5 km S Batavia Downs , flight intercept trap, 12° 41', 142° 41' E, 23 August–16 September 1992, P. Zborowski & L. Miller (2 ANIC) ; Hann River , 15° 11' S, 143° 52' E, 16 August 1992, P. Zborowski & J. Cardale (1 ANIC) ; Leichart Creek, 8k N Bluewater , 19° 10' S, 146° 32' E, 18 December 2002, A. J. & C. H. S. Watts (2 SAMA) ; Western Australia: 14 km SbyE Kalumburu Mission, CALM Site 4/3 [Western Australian Department of Conservation and Land Management], at light, open forest, 14° 25' S, 126° 40' E, 3–6 June 1988, T. A. Weir (2 ANIC) ; Synnot Ck., CALM Site 25/1 [Western Australian Department of Conservation and Land Management], at light, open forest, 16° 31' S, 125° 16' E, 17–20 June 1988, T. A. Weir (1 ANIC) . Representative specimens to be deposited in MCZ and NPC.

Differential Diagnosis. A very distinctive species, recognized by the small size, the squamiform dorsal setae, and the wide fringe of arcuate setae on the elytral lateral margins (Fig. 66). Similar to G. nanosetus (Fig. 64) in having the abdominal hydrofuge pubescence reduced to the first two ventrites, but differing in smaller size, more distinctly widened (squamiform) dorsal setae, wider fringe of setae on the elytral margins, larger elytral punctures, confluent anterior­posterior pronotal foveae, and the reduced abdominal hydrofuge pubescence, covering ventrite 1 and present basolaterally on ventrite 2. The male genitalia of the two species are quite dissimilar (Figs. 65, 67).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.26/ 0.56; head 0.30/0.37; pronotum 0.30/0.48; elytra 0.82/0.56. Form moderately ovate, moderately convex. Dorsum dark brown, weakly shining beneath distinctive whitish or yellowish setae.

Head with dorsum clothed in distinctive decumbent setae, setal sockets minutely raised; frons very sparsely punctate; interocular foveae deep; interocular tuberculi distinct; basomedial fovea narrowly confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength about 0.5 apical width, non­punctate (but setal sockets minutely raised). Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum at angle to clypeus, only very small apicomedian tooth visible in habitus view; width twice length. Maxillary palpomere 3 about twice length of 4.

Pronotum distinctively setose; lateral hyaline border well developed, origin at base of lateral depression, lateral margin angulate, then continuous with very narrow posterior hyaline border; anterior margin of pronotum arcuate between lateral depressions; each lateral depression with posterior angle acute, lateral margin straight, densely clothed in long setae which form a fringe equal to 0.5 width of lateral depression; lateral fossulae deep; pronotal disc moderately convex, with short flattened narrow setae that taper from base to apex; median groove narrow, deeper in front and behind midlength, constricted in midlength, not attaining anterior and posterior margins, tapering at ends; anterior foveae well developed, transverse; posterior foveae oblique, shallow, oval, nearly attaining anterior foveae; posterolateral angles lacking impressions.

Elytra clothed in distinctive decumbent flattened setae that taper from base to apex; setae serial, forming six rows between suture and humeral angle; punctures on disc large, transverse, obliterating intervals; elytra convex on disc; summit of posterior declivity at about midlength; elytral explanate margin very narrow, with fringe of long arcuate setae, those in anterior 0.5 of elytron twice as long as pronotal fringe.

Metasternal glabrous area length less than width (as 10:12), subrhomboidal, shining, convex. Abdominal ventrites 1 and basolaterally 2 with hydrofuge pubescence.

Aedeagus (Fig. 67): Length of main­piece 0.20 mm, length to tip of parameres 0.21 mm; lobes relatively short, weakly subapically barbed; apical paramere seta longer than other setae.

Females unknown.

Etymology. Named in reference to the widened and flattened dorsal setae.

Distribution. A wide northern distribution pattern, found north of about 20° S. latitude, with widely separated locality records in Western Australia, Northern Territory, and Queensland (Fig. 74).