Gymnochthebius hesperius, 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 hesperius new species

(Figures 19, 20, 73)

Type Material. Holotype (male): Australia: Western Australia: Lyndon R. Bridge, 23° 36' S, 113° 51' E, 13 August 1975, K. & E. Carnaby. Deposited in the ANIC . Paratypes (36): Australia: Western Australia: 10 km NW Eerala Stn., 21° 19' S, 117° 2' E, 23 May 2001, C. H. S. Watts (3 SAMA); Carine, Perth, grass pile, 31° 51' S, 115° 46' E, 1–30 May 1983, V. Lorimer (1 AMSA); L. Walyungup, 32° 20' S, 115° 46' E, 1–30 March 1972, P. Zwick (9 MCZ); Lyndon R. Bridge, 23° 36' S, 113° 51' E, 13 August 1975, K. & E. Carnaby (13 ANIC); Millstream, shallow stream, from gravel at edge of pool at pipe crossing, 21° 35' S, 117° 4' E, 2 November 1970, E. Britton (1 ANIC); Murchison R., 27° 49' S, 114° 41' E, 28 March 1971, E. F. Riek (2 ANIC); Wooramel River , Callytharra Springs Stn, 25° 49' S, 115° 22' E, 20 May 2001, C. H. S. Watts (3 SAMA); same locality, 25° 49' S, 115° 22' E, 26 May 2001, C. H. S. Watts (4 SAMA). Representative specimens to be deposited in MCZ, NMW, NPC, and WAMP .

Differential Diagnosis. Recognized by the relatively large eyes and large elytra, the black head contrasting with the primarily testaceous body, the pronotal disc with foveae large and microreticulate, contrasting with the finely sparsely punctate and shining reliefs, and the abdominal hydrofuge pubescence restricted to ventrites 1–2 and basolaterally on 3. This species is very readily distinguished from the somewhat similar G.clarki by the larger body size (ca. 1.70 mm vs. 1.57 mm), the smaller pronotum (in relation to the elytra), the much more finely sparsely punctate and shining pronotal reliefs and the with deeper and larger foveae, and the color differences. The male genitalia of the two species distinctly differ in several features; in G. hesperius the parameres are longer and wider, the lobes each have a barb near the apex, and the duct is enlarged apically ( Figs. 14 , 20).

Description. Size (length/width, mm) holotype: body (length to elytral apices) 1.70/ 0.73; head 0.33/0.44; pronotum 0.37/0.56; elytra 1.07/0.73. Form moderately ovate, mod­ erately convex. Elytra and legs testaceous, pronotum testaceous laterally, darker medially, head black. Head and pronotal reliefs highly shining, elytra less so.

Head with eyes relatively large in dorsal aspect; frons very finely sparsely punctate, very sparsely pubescent; interocular foveae deep, effacedly microreticulate; interocular tuberculi distinct; basomedial fovea narrowly confluent with interocular foveae. Frontoclypeal suture deeply impressed, arcuate. Clypeus midlength:apical width 3:5, very finely sparsely punctate; pubescence very sparse on disc, slightly more developed laterally; anterior margin arcuate toward rear and edge upturned to form low ridge. Labrum length:width 2:5, subtriangular in dorsal aspect, apicomedian tooth upturned.

Pronotum lateral hyaline border well developed, origin at base of lateral depression, very weakly arcuate to posterior angles, very narrow around posterior margin; anterior margin of pronotum arcuate in midregion; each lateral depression with posterior in form of right angle, lateral margin arcuate, with fringe of short setae; lateral fossulae deep, microreticulate; pronotal disc moderately convex, reliefs highly shining, extremely finely sparsely punctate, fovea dull, microreticulate; each puncture on reliefs with an extremely small recumbent yellow seta; median groove moderately deep, constricted just behind midlength, forming narrow channel, extending nearly to margins, tapering at ends; anterior foveae well developed; posterior foveae oblique, oval impressions nearly 1/2 as long as and twice as wide as widest part of median groove; posterolateral angles each with distinct shallow impression.

Elytra moderately wide, weakly convex on disc, with six rows of punctures between suture and humeri; serial punctures moderately coarse, closely spaced; intervals weakly rounded, as wide as punctures; summit of declivity near apical 1/4; striae 2 and 3 terminating into 4 at about apical 1/4; intervals 4 and 5 slightly swollen at posterior declivity; elytral margin lacking prominent setae; explanate margin narrow, present over middle 0.5.

Metasternal glabrous area length about equal width, widest before midlength, suboval, shining, with a few punctures. Abdominal ventrites 1–2 and basolaterally 3 with hydrofuge pubescence.

Aedeagus (Fig. 20): Length of main­piece 0.28 mm, length to tip of parameres 0.31 mm; main­piece widened near midlength in lateral aspect, widened at base of lobes in ventral aspect; lobes relatively long, tapering rather abruptly, each with a very small barb subapically on ventral surface; dorsal notch U­shaped, wider than V­shaped ventral notch which is slightly deeper and slightly narrowed apically; duct enlarged apically; parameres in ventral aspect widened on inner surface apically, in general wider in lateral aspect than in ventral aspect, apical seta elongate, ca. 2x length of next longest seta.

Females have the elytral explanate margin slightly wider than that of males; the anterior margin of the labrum is arcuate.

Etymology. Named in reference to the western distribution.

Distribution. Currently known from western Western Australia (Fig. 73).

Figures

FIGURE 14. Gymnochthebius clarki. Aedeagus (drawn from holotype of G. angustipennis (Deane), junior synonym).