Ochthebius sitiensis, Perkins, Philip D., 2011

Perkins, Philip D., 2011, New species and new collection records of aquatic beetles in the genus Ochthebius Leach from southern Africa (Coleoptera: Hydraenidae), Zootaxa 3093, pp. 1-34 : 7-10

Ochthebius (s.s.) sitiensis , new species

( Figs. 3 , 4, 26 )

Type Material. Holotype (male): Namibia: Okau Fountain, 12.5 km inland, spring and narrow running stream, fairly saline, in reeds, 18° S, 12° E, 22 i 1983, Bethune and Day ( SMW). Paratypes (44): Namibia: Fish R. Canyon, moist gravel in stream bed, 27° 37' S, 17° 36' E, 12–14 i 1972, Southern African Exp. BM (35 NHM); Hunkab River, ca. 44 km inland, saline stream with some reeds, 19° ' S, 13° ' E, 25 i 1983, Bethune and Day (1 SMW); Okau Fountain, 12.5 km inland, spring and narrow running stream, fairly saline, in reeds, 18° S, 12° E, 22 i 1983, Bethune and Day (8 SMW).

Differential Diagnosis. This species is quite similar in dorsal habitus to O. bicomicus ; both have very coarsely and confluently punctate pronotal foveae ( Figs. 3 , 9 ). Reliable determinations will be based on examination of the aedeagi, which distinctively differ in shapes of the main piece and the distal piece ( Figs. 4, 10).

Description. Size: holotype (length/width, mm): body (length to elytral apices) 1.77/0.82; head 0.32/0.47; pronotum 0.46/0.64, PA 0.54, PB 0.55; elytra 1.11/0.82.

Color: Head black, weakly aeneous; pronotum brown to dark brown except lighter brown narrowly along base; elytra brown to light brown, columellae of serial punctures dark brownish; antennae, maxillary palpi and legs, except coxae, bright stramineous, contrasting sharply with dark brown Venter: Head: Eyes rather small, in dorsal aspect 8 weakly convex facets in longest series. Frons shining, distinctly but finely sparsely setiferously punctate, punctures ca. 0.5xef or smaller, setae recumbent, setal length and interstices both 1–3xef but denser near eyes; interocular foveae large, round, deep, width of each about equal distance separating them, each internally with few setiferous punctures. Clypeus strongly shining, disc weakly convex, laterally weakly concave, sculpture very similar to frons, sides densely pubescent. Labrum shining, very finely setiferously punctate; anterior margin apicomedially upturned to form small tooth, area behind tooth weakly concave. Pronotum: Subcordate, widest just behind anterior angles; anterior margin very weakly bisinuate, without postocular emarginations, with very small postocular processes, hyaline border well developed; sides sinuately attenuate to posterior angles; rather wide lateral hyaline border beginning just behind anterior angles, edge weakly arcuate or straight over median 0.8, continuing around basal angles and along base. Disc with anterior impression deep, T-shaped, midlongitudinal extension nearly attaining posterior impression, outer edge of impression gradually sloping; posterior transverse impression slightly larger and deeper, slightly arcuate, with three deeper areas; disc longitudinally slightly convex between foveae; impressions densely coarsely punctate, subrugose; reliefs shining, coarsely densely punctate but size and spacing of punctures quite irregular, size 1–3xef, smaller in middle of disc, interstices with exceedingly fine and sparse micropunctulate ground sculpture. Lateral depressions subrugosely strongly punctate, slope continuing transverse curvature of disc but appearing slightly inflated. Setae of discal punctures recumbent, fine and very indistinct. Elytra: Widest at middle, sides arcuate, explanate margin narrow in male, about equal to greatest width of tarsus, wider in female. Apices narrowly conjointly rounded in both sexes. Ten-seriate punctate, series not at all striate-impressed except sutural series behind middle, on disc punctures well impressed, slightly larger than largest pronotal punctures, ca. 3xef, interstices ca. 0.5–1xpd, only a few punctures with a perceptible minute granule at anterior margin, distally punctures progressively smaller and more longitudinally separated. Intervals flat, very weakly shining, subalutaceous, ca. 0.5–1xpd. Serial setae fine decumbent and short, each attaining base of next seta in series; nervure setae indistinct. Venter: Mentum shining, moderately sparsely setiferously punctate. Metaventrite pubescent laterally, disc with large, subtriangular, strongly shining area, glabrous except few setiferous punctures anteriorly. Abdominal ventrites 1–5 entirely clothed with dense hydrofuge pubescence; 6 effacedly microreticulate, weakly shining.

Variation. Some of the specimens from the Fish River Canyon have the maxillary palpi and legs darker than those of the northern populations. The distal piece of the aedeagus on specimens from this locality are shaped slightly differently than the holotype, having the tip slightly narrower; the shape of main-piece is virtually the same in all specimens. Most specimens are about the same size as the holotype (1.77 mm); the smallest male examined was 1.41 mm.

Etymology. "Living in a thirsty place."

Distribution. Currently only known from Namibia, with two northern localities and one disjunct, far southern locality ( Fig. 26 ).

Figures

FIGURE 3. Ochthebius sitiensis, dorsal and lateral habitus of holotype.

FIGURE 9. Ochthebius bicomicus, dorsal and lateral habitus of holotype.

FIGURES 25 – 28. Geographical distributions of Ochthebius. 25. O. namibiensis. 26. O. sitiensis. 27. O. bupunctus. 28. O. extremus.