Gymnochthebius perpunctus, 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 perpunctus new species

(Figures 58, 59, 88)

Type Material. Holotype (male): Australia: South Australia: Somme Creek , bn Angaston & Sedan, gravelly cobble­bank at small creek in pasture, elev. 420 m, 34° 34' S, 139° 9' E, 2 March 2000, N. Porch (62). Deposited in the ANIC . Paratypes (52): Australia: South Australia: 9.6 km N of Hawker, at light, 31° 48' S, 138° 25' E, 29 February 1972, E. G. Matthews (1 SAMA); Adelaide [no date], 34° 55' S, 138° 36' E, P. D. Morris (4 BMNH); Chambers Gorge, 30° 58' S, 139° 16' E, 1–30 September 1983, C. Watts (6 SAMA);); Flinders Range [date = “96”], Denton (1 NMW); Gilbert River Stockport , 34° 20' S, 138° 44' E, 5 October 1994, Aust. water quality centre 3448 (2 SAMA); Hookina Ck Mt. Little, 31° 44' S, 138° 24' E, 15 November 1994, Aust. water quality centre 3636 (2 SAMA); Murray River , shore washing, 34° 57' S, 139° 16' E, 27 November 1982, Endrödy­Younga (AU­13) (11 TMSA); Nooltana Ck . 13 km NNW Hawker, 31° 47' S, 138° 22' E, 17 May 1981, J. A. Forrest (2 SAMA); Salt Ck at Mangalo, 33° 32' S, 136° 37' E, 10 November 1994, Aust. water quality centre 3686 (1 SAMA); Somme Creek , bn Angaston & Sedan, gravelly cobble­bank at small creek in pasture, elev. 420 m, 34° 34' S, 139° 9' E, 2 March 2000, N. Porch (62) (22 ANIC). Representative specimens to be deposited in MCZ, MVMA, NPC, QMBA, and WAMP .

Differential Diagnosis. Recognized by the strongly punctate dorsum, the elytral serial punctures deep and serially contiguous, the intervals appearing zig­zag due to large serial punctures, and the large, rhomboidal, sub­tabelliform metasternal glabrous area. Distinguished from the somewhat similar G. rhombus by the larger size (ca. 1.93 mm vs. 1.53 mm), the more strongly punctate pronotum, with punctures obscuring the margins of the discal foveae, and the narrower elytral setae (Figs. 58, 60). The male genitalia of the two species also show a relationship, but G. perpunctus differs in having the lobes wider, more apically rounded and with a minute barb, the duct wider compared with the width of the parameres, and the paramere setae longer compared with the width of the notch (Figs. 59, 61).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.93/ 0.82; head 0.37/0.48; pronotum 0.48/0.63; elytra 1.22/0.82. Form moderately ovate, moderately convex. Color dark brown, dorsal surface strongly punctate, weakly shining between punctures.

Head with moderately dense whitish setae; frons densely coarsely punctate; interocular foveae deep; interocular tuberculi distinct; basomedial fovea narrowly confluent with interocular foveae. Frontoclypeal suture deeply impressed, bisinuate. Clypeus midlength 0.5 apical width, densely coarsely punctate. Labroclypeal suture straight in dorsal view, evenly arcuate in anterior view. Labrum width:length as 15:6, anterior margin arcuate, without apicomedian tooth.

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 arcuate in midregion; each lateral depression with posterior angle produced to acute point, lateral margin weakly arcuate from anterior angle, weakly emarginate in front of posterior angle, with short fringe of setae; lateral fossulae deep, microreticulate; pronotal disc moderately convex, coarsely densely punctate, very effacedly microreticulate on reliefs, more strongly microreticulate in foveae; each puncture with a recumbent whitish seta which contrasts with dark cuticle; median groove narrow, deep, extending nearly to margins; anterior foveae large, deep; posterior foveae oblique, 1/2 as long as and twice as wide as median groove; posterolateral angles strongly punctate, without impressions.

Elytra convex on disc, with six rows of large, deep, serially contiguous punctures between suture and humeri, each puncture with a distinctive decumbent whitish seta; intervals narrower than punctures, zig­zag; posterior declivity abrupt, summit near apical 0.33; striae 2 and 3 terminating into 4 at about apical 0.15; elytral explanate margin narrow, lacking prominent fringe setae.

Metasternal glabrous area length equal width, rhomboidal, subtabelliform, anteriorly attaining mesosternal intercoxal process, sparsely punctate. Abdominal ventrites 1–3 and minutely basally 4 with hydrofuge pubescence.

Aedeagus (Fig. 59): Length of main­piece 0.29 mm, length to tip of parameres 0.32 mm; lobes moderately long, apically arcuate in ventral aspect, truncate in oblique aspect, each with a very minute barb subapically; notches U­shaped, nearly parallel­sided, slightly wider than lobes, dorsal slightly deeper than ventral; duct nearly straight, not expanded apically; apical paramere seta elongate, ca. 2x length of next longest seta.

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

Etymology. Named in reference to the markedly punctate dorsum.

Distribution. Currently known from southern South Australia (Fig. 88).