Usia biconvexa Gibbs, 2011

Gibbs, David, 2011, 2960, Zootaxa 2960, pp. 1-77 : 24-26

Usia biconvexa Gibbs sp. nov.

( Figs. 17 & 19, Plate II)

Type material examined. HOLOTYPE: Israel, Yavne Rt. 4, 15 April 1994, A. Freidberg & Fini Kaplan [♂ in TAU] . PARATYPES: Israel, Yavne Rt. 4, 15 April 1994, A. Freidberg & Fini Kaplan [2♀ in TAU]; Nizzanim Beach , stable coastal dunes 43m. el, 15 April 1995 M.E. Irwin, N31º44.21' E34º36.89' [♂ 2♀ in TAU]; Nizzanim Park, 13 April 2008, A. Freidberg [♀ in TAU]; 18 April 2008 [2♀]; 21 April 2008 [♀ in TAU] .

Etymology. Name derives from the Latin “ bis = two or double, convexus = arched”, refers to the gonocoxite when viewed from above, which forms two hemispheres deeply divided medially.

Diagnosis. A small entirely black species, teneral or faded specimens browner; so far only known from Israel. Most individuals will be identifiable by a combination of short adpressed hairs on ventral side of hind femora, hairs on margin of scutellum about as long as length of scutellum medially. Male epandrium very large and elongate, placed at 90º to axis of abdomen, significantly larger than the abdomen, almost entirely bare. Female cerci remarkably developed, shining, rhomboidal, enclosing the tip of the apical sternite which is strongly raised proximally to form a transverse ridge which drops off very steeply on proximal side. Details of male and female genitalia diagnostic (Plate II).

PLATE II. Usia biconvexa 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 furca lateral, i female sternite 8 ventral, j female sternite 8 lateral.

Description. Measurements. Body length. 2.0– 2.4mm Wing length. 2.1–2.8mm.

Male. Head. Frons relatively broad, about a quarter head width, at narrowest point as wide or wider than length third antennal segment, rather matt but without discrete grey dust spots, front of frons close to antennal bases often obscurely brown. Mouth margin exceedingly narrow, almost disappearing below, above near antennae very thinly dulled by dust. Ocellar triangle obtuse, lateral ocelli separated from the eye by their diameter. Longest hairs on ocellar tubercle about as long as width across frons at vertex or a little longer. Occiput covered with grey dust obscuring ground colour, marginally more thinly so on triangular area behind vertex. Black hairs on occiput short above, longer below, those on ventral side of head as long as the hairs on ocellar tubercle. Antennae black, relatively short, third antennal segment obovate, about twice as long as scape and pedicel combined. Antennae lacking the usual dorsal setulae. Proboscis black, naked, relatively short, about as long as mesonotum. Palps small, black to brown, subclavate with small apical setae. Thorax. Entirely black, mesonotum shining and mostly smooth to inconspicuously wrinkled with hair insertions not strongly marked, thinly dusted on pronotum, postpronotal lobe, notopleuron and posterior part of mesonotum adjacent to scutellum. Mesonotum with long, scattered, perpendicular black hairs, acrostichals biserial, clearly separated by bare paramedian lines from generally distributed lateral hairs, the longest longer than length of third antennal segment. Scutellum smooth, surface thinly dusted, disc bare, hind margin with a somewhat irregular, in parts uniserial, row of long, upwardly directed black hairs the longest as long as scutellum is long. Pleura black to dark brown, predominantly subshining but with thin dusting covering most of anepisternum. Posterodorsal part of anepisternum with shortish dark hairs. Wing. Clear, the veins pale yellowish brown. Anal lobe convex, a little wider than anal cell, r-m before middle of discal cell. Haltere. Whitish knob, stem slightly infuscated basally. Legs. Black to dark brown, shining but with rough texture to cuticle, with very short, adpressed black hairs, those on the femora generally longer than those on tibia. Tarsi shorter than respective tibia, segments 2–4 short and almost equal in length, together a little longer than basitarsus. Abdomen. Black, short with broad tergites, surface sculpture obscure, no more than inconspicuous hair insertions. Basal tergites dulled by a thin coating of pale dust. Disc of tergites covered with relatively short black hairs, much longer hairs laterally. Sternites similar but difficult to see. Genitalia. Very large and elongate, placed at 90º to axis of abdomen, significantly larger than the abdomen and often completely obscuring the sternites. Epandrium evenly convex with apical triangular extensions folded around the cerci, almost entirely hairless. Viewed dorsally lobes of gonocoxite conspicuous, deeply divided such that the two halves form two almost separated hemispheres. Gonocoxite with perpendicular black hairs as long as any elsewhere on the insect. The simple, curved gonostyli often visible in pinned specimens but can be enclosed in apical part of epandrium. Tip of epiphallus with claw-like spine and spiny structure as in U. carmelitensis .

Female. Very like male, frons a little wider, mouth margin very slightly broader, generally shorter haired and tarsi not so clearly shorter than tibia. Tergites dulled by dust with a rather greasy appearance. Cerci remarkably developed, shining, rhomboidal with an apical and ventral fringe of setulae. These enlarged cerci enclose the tip of the apical sternite which itself is characteristically structured. In pinned material this sternite is strongly raised proximally to form a transverse ridge which drops off very steeply on proximal side. When dissected the apical processes (sternite 9) can be seen to be well developed, shiny plates that mirror the well developed cerci.

Discussion. The epiphallic complex clearly show the affinities of this species with U. carmelitensis and U. dahli .

Distribution. Israel. So far only known from eleven specimens from the coastal plain south of Tel Aviv, Israel, so appears to be scarce, very local and potentially endangered.