Gymnochthebius minipunctus, 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 minipunctus new species

(Figures 56, 57, 76)

Type Material. Holotype (male): Australia: Northern Territory: Palm Valley , 24° 4' S, 132° 45' E, 1–30 April 1968, C. Watts. Deposited in the SAMA . Paratypes (196): Australia: New South Wales: Wilcannia, 5 km E of, at Darling River , sandy mud at edge of river, elev. 70 m, 31° 34' S, 143° 25' E, 1 September 2000, N. Porch (5) (5 ANIC) ;

Northern Territory: Finke Gorge NP ( Boggy Hole ), large permanent pool in river bed, grassed and bulrushes at edge, algal growth, 24° 9' S, 132° 52' E, 15 March 1995, T. Weir (9 ANIC) ; Finke Gorge NP (Kanara Ck. at The Oasis ), permanent rock pools, palms, grass at edges, algal growth, 24° 4' S, 132° 44' E, 12 March 1995, T. Weir (1 ANIC) ; Finke River at Glen Helen Gorge, West Macdonnells NP, flowing river, large pools, with bulrushes, sandy bottom, algal growth, 23° 41' S, 132° 40' E, 10 March 1995, T. Weir (1 ANIC) ; Finke River at Running Water , at light, 24° 20' S, 132° 53' E, 15 March 1995, T. Weir (1 ANIC) ; Finke River at Running Water , temporary pools in sandy creek bed, 24° 20' S, 132° 53' E, 15 March 1995, T. Weir (6 ANIC) ; Finke River xing, Stuart Highway , flowing river (temporary), sandy base, over­hanging vegetation, 24° 33' S, 133° 14' E, 4 March 1995, T. Weir (2 ANIC) ; Hugh River , 12.5 km SSE of Paisley Bluff, flowing river, deep pool, grass at edges, sandy bottom, 23° 49' S, 133° 22' E, 7 March 1995, T. Weir (2 ANIC) ; Palm Valley , 24° 4' S, 132° 45' E, 1–30 April 1968, C. Watts (18 SAMA) ; Simpson Gap, West Macdonnells NP, large pools in flowing creek (temporary) with grass at edge, 20° 40' S, 133° 43' E, 6 March 1995, T. Weir (1 ANIC) ; Queensland: Boulia , 22° 54' S, 139° 54' E, 1–30 July 1972, C. Watts (2 SAMA) ; Cape River , 100 km S Charters Towers, river, 21° 0' S, 146° 25' E, 12 December 2002, C. H. S. Watts (1 SAMA) ; Dalrymple , 30 km N Charters Towers, elev. 300 m, 19° 49' S, 145° 44' E, 18 January 1993, Wewalka (2 NMW) ; Pioneer R. nr. Mirani , 21° 9' S, 149° 13' E, 4 September 1972, H. E. Hinton (1 ANIC) ; South Australia: 3 km N Portee Stn. R. Murray , small river nat depression, 34° 24' S, 139° 36' E, 19 March 1973, G. F. Gross (2 SAMA) ; Murray River [no date], river, 34° 57' S, 139° 16' E, A. H. Elston (15 AMSA) ; Murray River , shore washing, 34° 57' S, 139° 16' E, 27 November 1982, Endrödy­Younga (AU­13) (35 TMSA) ; R. Murray , 34° 57' S, 139° 16' E, 1–30 December 1917, R. J. Burton (1 SAMA) ; Small billabong nr. Mannum , 34° 55' S, 139° 18' E, 29 June 1976, R. Shiel (4 SAMA) ; Victoria: Lake Hattah , 34° 44' S, 142° 21' E, 28 February 1967, G. W. Anderson (1 ANIC) ; Loddon River at Newstead , gravel at edge of small river flowing through pasture, elev. 210 m, 37° 6' S, 144° 3' E, 27 November 1999, N. Porch (47) (67 ANIC) ; McKillops Bridge, Snowy River , gravel at edge of large and rising river; dry sclerophyll forest, elev. 185 m, 37° 5' S, 148° 23' E, 6 November 2000, N. Porch (NP 16) (4 ANIC) ; Murray River [no date], 34° 57' S, 139° 16' E, not given (7 SAMA) ; Sea Lake [no date], 35° 29' S, 142° 50' E, Goudie (1 UQIC) ; Wimmera River at Western Highway , muddy sand at edge of river pool in dry sclerophyll/riverine forest, elev. 100 m, 36° 25' S, 141° 58' E, 1 March 2000, N. Porch (61) (1 ANIC) ; Wyperfeld National Park, Frew’s Plain , at light, 35° 37' S, 142° 1' E, 15–17 November 1973, S. Misko (4 ANIC) ; Western Australia: 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 AMSA, BMNH, CMNH, FMNH, MCZ, MVMA, NPC, QMBA, and WAMP .

Differential Diagnosis. Recognized by the markedly microreticulate head and pronotal foveae, the pronotal reliefs sparsely but distinctly punctate over effacedly microreticu­ late ground sculpture, the striate­impressed elytral series, the abdominal ventrites 1–2 and basal part of 3 with hydrofuge pubescence, and the brown dorsum with metallic reflections. The male genitalia have the apices of the lobes shaped similar to those of G. angulonotus , but other features of the genitalia differ ( Figs. 6 , 57), and the two species differ markedly in habitus ( Figs. 5 , 56).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.75/ 0.63; head 0.37/0.44; pronotum 0.37/0.56; elytra 1.07/0.63. Form moderately ovate, moderately convex. Pronotum and elytra brown with slight metallic reflections, head black, entire dorsal surface dull.

Head microreticulate; interocular foveae deep; interocular tuberculi distinct; basomedial fovea narrowly confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength about equal apical width, very sparsely pubescent laterally. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum width twice length, anterior margin with small apicomedian tooth. Maxillary palpomere 3 slightly greater than twice length of 4, slightly swollen.

Pronotum with impressions strongly microreticulate, reliefs effacedly microreticulate; lateral hyaline border well developed, origin at base of lateral depression, weakly arcuate to posterior angles, very narrow around posterior margin; anterior margin of pronotum slightly produced in midregion; each lateral depression with posterior angle about right, not produced in acute point, lateral margin arcuate, setose; lateral fossulae deep; pronotal disc moderately convex, reliefs sparsely but distinctly punctate over effacedly microreticulate ground sculpture, some punctures with short indistinct recumbent seta; median groove moderately deep and wide, slightly narrowed in midlength, extending nearly to margins, tapering slightly apically, widening slightly basally; anterior foveae large and deep, wider than median groove; posterior foveae oblique, deep linear impressions slightly greater than 1/2 as long as and nearly twice as wide as median groove; posterolateral angles with indistinct shallow impressions.

Elytra moderately convex on disc, with six rows of closely spaced slightly elongate punctures in well developed striae between suture and humeri; intervals rounded, width about equal that of punctures; summit of declivity slightly behind midlength; striae 2 and 3 terminating into 4 at about apical 1/4; elytral explanate margin narrow, lacking prominent setae.

Metasternal glabrous area length less than width (as 15:20), subrhomboidal, shining, very sparsely punctate, convex. Abdominal ventrites 1–2 and basal part of 3 with hydrofuge pubescence.

Aedeagus (Fig. 57): Length of main­piece 0.26 mm, length to tip of parameres 0.28 mm; lobes moderately long, in oblique view each lobe pointed at apex and with small barb of similar size near apex; dorsal notch U­shaped, wider than V­shaped ventral notch; duct large compared to notch, apically truncate in lateral aspect; apical paramere seta elongate, ca. 2–3x length of next longest setae.

Females have the elytral explanate margin similar to that of males; the anterior margin of the labrum is weakly apicomedially emarginate.

Etymology. Named in reference to the distinctive microsculpture.

Distribution. A widely distributed species, being found in portions of Victoria, South Australia, western New South Wales, southern Northern Territory, Queensland, and one locality in Western Australia (Fig. 76).

Figures

FIGURE 5. Gymnochthebius angulonotus, holotype. Dorsal and lateral habitus.

FIGURE 6. Gymnochthebius angulonotus. Aedeagus of holotype.