Usia dahli Gibbs, 2011

Gibbs, David, 2011, 2960, Zootaxa 2960, pp. 1-77 : 33-35

Usia dahli Gibbs sp. nov.

(Plate VI)

Usia (?) pusilla: Theodor, 1983: 62 , Figs. 168–170, misidentification.

Type material examined. HOLOTYPE: Tunisia, Kartago , 24 April 1973 [leg. R.] Dahl / Pres. by R. Dahl, BMNH(E) 1997-240 [♂ in BMNH] . PARATYPES: Algeria, La Calle, Le Boul / Usia / n.sp./ Museum Paris, Coll. E Séguy 1919 [♀ in MNHN]; Philippeville, Algérie, A. Thery [♀ in MNHN; ♂ in TAU] . Tunisia, Kartago, 24 April 1973 [leg. R] Dahl / Pres. by R. Dahl, BMNH(E) 1997-240 [♀ in BMNH]. Monastir, salin, 25 April 1973 [leg. R.] Dahl / Pres. by R. Dahl, BMNH(E) 1997-240 [♀ in BMNH]; Tabarka , dunes 13 May 1995 / Tunisia, J.C. Deeming, NMW.Z, 1995:026/ Usia pusilla det M.J. Ebejer ’96/ NMW.Z 1981.001 [♀ in NMWC]; Mahadia , dunes N of Chebba 0m, N35º18'24.28" E11º3'16.12", 28 April 2009, leg. D.J. Gibbs [2♀ in PCDG] .

Etymology. Named after Richard Dahl who collected the holotype and two of the paratypes.

PLATE VI. Usia dahli Gibbs sp. n.; a epiphallic complex ventral, b epiphallic complex lateral, c gonocoxite ventral, d gonocoxite lateral, e epandrium dorsal, f epandrium lateral, g female genitalia ventral, h female sternite 8 ventral.

Diagnosis. A small, compact, almost entirely black species very close to U. carmelitensis but confined to the eastern Maghreb. Hind femur with short, adpressed hairs, marginal hairs of scutellum as long as scutellum medially. Male with large, globular genitalia, gonocoxite medially with a pair of convergent processes tipped with setae, these often visible in pinned specimens. Female apical sternite strongly and evenly domed. From allopatric U. carmelitensis , only be details of genitalia (Plate VI).

Description. Measurements. Body length. 1.8–3.3 mm Wing length. 2.0– 3.1mm.

Male. Head. Frons relatively broad, at narrowest point as wide or wider than length third antennal segment, rather matt but without discrete grey dust spots, front of frons more brown. Mouth margin exceedingly narrow, practically absent, broader and browner level with antennae. Ocellar triangle obtuse, lateral ocelli separated from the eye by their diameter or a little less. Longest hairs on ocellar tubercle about as long as width across lateral ocelli. Occiput covered with grey dust, including area behind vertex which is slightly more shining, and black hairs, shorter above, long below. Antennae black, relatively short, third segment obovate, about twice as long as scape and pedicel combined, almost bare above. Proboscis black, naked, about as long as mesonotum. Palps very small, black with small apical setae. Thorax. Entirely black, mesonotum shining and mostly smooth, lightly grey dusted on pronotum and postpronotal lobe. Posterior part of mesonotum slightly wrinkled, Vestiture as long as that on vertex, evenly distributed such that distinct acrostichal and paramedian lines not discernable. Scutellum shining, but surface slightly roughened, disc sparsely haired, longer marginal hairs longer than scutellum is long. Pleurae black, predominantly shining, scattered hairs on rear part of anepisternum which is thinly dusted centrally. Wing. Clear to vaguely tinged brownish, veins brown. Anal lobe convex, as wide as anal cell. Haltere. Yellow knob, stem infuscated. Legs. Black, shining but with rough texture to cuticle, with very short, adpressed black hairs, more dense on tibia. Abdomen. Black, short with very broad tergites, rough surface sculpture, covered with relatively short black hairs. Genitalia. Almost as large as abdomen, but smaller than in some similar species. Epandrium long with blunt apico-lateral projections, often enclosing tip of gonocoxites. Gonocoxite short, with a pair of convergent processes tipped with setae medially, these often visible in pinned specimens. Epiphallic complex similar to that of carmelitensis but with tip of aedeagus conspicuously longer and clearly separated from the blunt process below it.

Female. Differs from the male only in wider frons, almost as wide as antennae is long, which widens more conspicuously towards the front. Mouth margin wider, as wide as the tips of the tiny palps. Abdomen shorterhaired, tapering to a rounded point. Apical sternite relatively large (although no as large as in carmelitensis ), basal two thirds strongly domed, transversely ridged, long scattered black hairs laterally, apical third with weak central ridge and shallow apical notch.

Discussion. This species is clearly very closely related to U. carmelitensis Becker. The absence of specimens from Libya and Egypt makes it impossible to rule out the possibility of a cline from east to west. However, given the material at hand, the two species are quite distinct in both sexes.

Distribution. Algeria, Tunisia. Specimens are few but include some recent ones; given the relative lack of collecting within its known range probably under recorded. Recent observations suggest that this species is quite common in the lowlands of Tunisia in April.