Usia accola Becker, 1906

Gibbs, David, 2014, A world revision of the bee fly tribe Usiini (Diptera, Bombyliidae) Part 2: Usia sensu stricto, Zootaxa 3799 (1), pp. 1-85 : 48-50

Usia accola Becker, 1906

( Figure 20 , Plate XI)

Usia accola Becker, 1906a: 14 [ 1906b: 214].

Type material examined. LECTOTYPE here designated; Tunisia, [locality indecipherable] 1896/ Tunis 40720/ accola Beck / Typus / Zool. Mus. Berlin. [♂ in ZMHB; excellent condition, head greasy].

Originally described from an unspecified number of specimens of both sexes in the Becker collection, now housed in ZMHB. However, only a single male syntype was located in ZMHB so this one becomes the lectotype.

Other material examined. Tunisia, Tabarka, 13 May 1995, 1♂, meadow, stream leg. M.J. Ebejer ( PCME) ; Cap Negro, 15 May 1995, ♀ leg. J.C. Deeming ( NMWC) ; Museum Paris, Tunisie, Ain-dhaham, H. Gadeau de Kerville 1908, May, June, Usia florea [♂] ( MNHN) ; Algeria, La Calle, W LeBoul, Usia florea , Museum Paris, Coll. E. Séguy 1919 [♂] ( MNHN).

Etymology. from Latin, meaning “near, nearby, a neighbour”.

Diagnosis. A large black, very short-haired species of northern Algeria and Tunisia. All shining black, the few available specimens lacking coloured reflections, all vestiture very short, more so than in sympatric species. Occiput shining and undusted behind upper eye margin, otherwise thinly grey dusted, hairs on ocellar tubercle shorter than distance between lateral ocelli, frons in front of anterior ocellus glabrous. Mesonotal vestiture very short and neat, very even in length, acrostichal setulae distinctly shorter than this line of hairs. Marginal scutellar hairs much less than half median length of scutellum. Anepisternum dusted on approximately posterior half. Genitalia small within the florea group, with epandrium longer than wide, apicolateral extensions square; furca with tip membranous.

Redescription. Measurements. Body length. 6.4–6.6mm. Wing length. 6.0– 6.2mm.

Male. Head. Oral margin narrow, almost linear although vanishing below shining black. Frons shining black, obliquely wrinkled posterolaterally, narrowest a little in front of anterior ocellus, approximately one fifth head width, distinctly wider than width across lateral ocelli, lateral ocellus separated from eye margin by one to two times the diameter of that ocellus. Frons grey dusted laterally on anterior half, the dust spots separated by an undusted area rather more than one third of the frons width at this point. Hairing very short, on ocellar area shorter than or a little longer than the diameter of a lateral ocellus, brown to dark brown, frons in front of anterior ocellus glabrous. Occiput shining black above adjacent to the eyes and on the depressed area behind the ocellar tubercle, thinly grey dusted centrally and below. White hairs covering occiput similar to those on mesonotum but a little longer especially below. Ommatidia uniform in size across the eyes. Antennae black, third segment longer than the scape and pedicel together, relatively narrow apically, swollen below basally, all segments with very short setae above. Sensilla small, brown and inconspicuous. Proboscis black, hairless, about as long as head and thorax together; palps short, dark brown, clavate with pale hairs, the longest conspicuously shorter than the length of the palps. Thorax. Mesonotum and scutellum shining black except for an area of light dusting on anterior slope between paramedian lines and post pronotal lobe, upper margin of post pronotal lobe and along lower notopleural area and above the wings. Cuticle smoother than in related species, hair insertions not conspicuous, on disc separated by their diameter or a little more. Bare paramedian lines extending back to about the mid point of the mesonotum, each a little narrower than the midline which has 5–6 irregular lines of hairs, uniform width throughout its length. Hind part of mesonotum slightly wrinkled medially close to scutellum, scutellum rather deeply, transversely wrinkled. Pleurae black with a covering of grey dust except approximately anterior half of anepisternum and an irregular patch in the middle of the anepimeron which are shining black and undusted.

Mesonotum and scutellum covered with very short whitish hairs, that on the disc of the mesonotum conspicuously shorter than the distance between the lateral ocelli, the majority of hairs overlapping by less than twice the distance between them. Posterior half of anepisternum and pronotum covered with rather longer whitish hairs. A few fine pale hairs on the middle of the katepisternum. Wing. Wing membrane conspicuously brownish yellow tinged anteriorly and basally, fading to a grey cast posteriorly and apically, the veins yellow, base of costa blackish. Anal lobe well developed with smoothly curved posterior margin, as broad as anal cell, crossvein r-m at or before middle of discal cell. Haltere. Yellow, becoming slightly brown at base of stem. Legs. Entirely black, the coxae grey dusted with fine white hairs on outer surface; femora shining, undusted with the longest pale ventral hairs barely longer than half the greatest width of a femur, tibia and tarsi with covering of minute dark setulae. Abdomen. Undusted black, lacking bronzy or bluish reflections, dulled by closely packed punctures that are joined by transverse furrows, the disc of the tergites covered with very short, whitish hairs barely overlapping each other. Laterally and on the down-curved margins the tergites are clothed with relatively longer, more yellowish hairs. Sternites also with similar long, pale yellowish hairs along their posterior halves. Genitalia. Prominent and conspicuous but smaller than in related species, shining black the gonocoxite covered in long, yellowish hairs similar to those on the lateral margins of the tergites, hairs on epandrium much shorter. In dried specimens the apex of the epandrium and lateral lobes of the gonocoxites are paler, in the lectotype yellowish. The characteristic shape of the gonostyli can often be seen in such specimens.

Female. As male except as follows: wider frons, shorter third antennal segment, hairs on down-curved margins of tergites shorter and paler. Apical sternite longer than wide, apically angled and with a median ridge. Furca with tip unpigmented, membranous, arms short and almost straight.

Discussion. This species is clearly very closely related to U. florea (Fabricius) and most of the few specimens seen have been misidentified as this species. However, the male genitalia are very different so they cannot be mistaken if the epandrium and aedeagus are examined. Probably even more closely related to the longer-haired U. atrata (Fabricius) and U. maghrebensis Gibbs , especially the latter which has similar male and female genitalia. U. florea and U. maghrebensis occur further west and are not known to be sympatric with U. accola but U. atrata can be found with this species in northern Tunisia.

Distribution. North east Algeria and adjacent northern Tunisia. The five specimens seen come from a small area either side of the Algeria-Tunisia border, none very far inland. Would appear to be rare and very range restricted.

Figures

FIGURE 20. ♀ U. accola anterior slope of mesonotum.