Usia calva Loew, 1869

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 : 29-30

Usia calva Loew, 1869

( Figure 19 , Plate IV)

Usia calva Loew, 1869: 250 .

Type material examined. LECTOTYPE here designated; Turkey, Bosdagh [=?Boz Dağlari near Izmir], Lederer/ calva sn./ 9690/ Coll. H.L. Loew/ Typus / Zool. Mus. Berlin [♀in ZMHB].

Originally described from an unspecified number of females. One syntype was found in ZHMB and is here designated as lectotype.

Other material examined. Turkey, vil. Eskisehir, 900m, 11 July 1972, M. e G. Osella leg. [♀ in CNBFVR].

Etymology. from Latin calvus for “bald” presumably referring to the mesonotum although it is merely shorter haired than most Usia , rather than naked.

Diagnosis. A medium sized species known only from two female specimens from two locations in western Turkey (location of lectotype not verified). All dark, aeneous black with a distinct greenish shine and very short, pale vestiture. Oral margin very narrow, almost linear, frons relatively narrow for a female Usia , about five times diameter of anterior ocellus, lateral ocelli separated from eye margin by a little more than its diameter, occiput shining black, dusted only on the two occipital ‘cushions’ or thinly grey-dusted below. Mesonotum evenly, and relatively densely, covered with short yellowish hairs (shorter than other Usia except lata and the quite different U. aeneoides ). Wings yellowish with anal lobe relatively convex, approximately the same width as the anal cell.

Redescription. Measurements. Body length. 5mm. Wing length. 4mm.

Male. Not seen.

Female lectotype. Head. Oral margin very narrow, almost linear, frons relatively narrow for a female Usia , widening slightly and evenly towards the front, about five times diameter of anterior ocellus, lateral ocelli separated from eye margin by a little more than its diameter. Frons shining black, only narrowly whitish dusted laterally in anterior half. Pale hairs on ocellar tubercle very short, shorter than the distance between the lateral ocelli. Occiput shining black, dusted only on the two occipital ‘cushions’ (thinly pale dusted below in the non-type specimen); covered with relatively short pale yellow hairs. Proboscis black, hairless above, a little shorter than head-thorax length; palps dark, very short with short, pale hairs. Antennae blackish, elongated and relatively slender. Thorax. Mesonotum shining aeneous black with a very small patch of grey dust above the wing base and dorsal margin of post pronotal lobe. Between the numerous hair insertion punctures, the surface of the mesonotum wrinkled, especially on the anterior slope either side of the paramedian stripes, laterally and adjacent to scutellum, the disc smooth between simple punctures. Paramedian lines short, about a fifth the mesonotal length, transversely wrinkled, narrower than mid-line which has about 5 rows of hairs. Scutellum transversely wrinkled, the hair insertions not conspicuous; posterior face rugosely sculptured. Mesonotum evenly, and relatively densely, covered with short yellowish hairs (shorter than other Usia except lata and the quite different U. aeneoides ), these hairs with a tendency to lean towards the middle of the mesonotum. Anepisternum shining black anteriorly, grey dusted on posterior margin, posterior half with a scattering of short whitish hairs. Remaining pleurae lightly grey dusted, not entirely obscuring the dark ground colour, pronotum with white hairs but katepisternum bare. Wing. Membrane clear, slightly yellow tinged, veins yellow basally becoming browner beyond middle. Anal lobe relatively convex, approximately the same width as the anal cell. Crossvein r-m at middle of discal cell. Halter . Pale yellow, slightly darker on base of stem. Legs. Entirely blackish, the coxae partially thinly grey dusted, both femora and tibia covered in short white hairs. Abdomen. Dark aeneous, tergites with a distinct green shine in type (blackish in the non-type specimen), densely covered by raised hair insertions which form a rough, transversely wrinkled texture, most dense on anterior third of each tergite. Tergites undulating, anteriorly convex, posteriorly concave (as in U. lata and U. anatoliensis ) Hairs short and whitish, longest on down-curved margins of the tergites. Sternites black dulled by a thin dusting, covered by whitish hairs, longer and less dense that those on the tergites. The furca of the non-type specimens differs from that of the type illustrated in that the tip is entire (lacks a transparent triangular ‘window’), and the vaginal plate, while equally long, tapers more evenly coming to a point so more triangular in shape.

Discussion. With only two specimens seen during this study and no males known, the possibility that these are aberrant examples or represent hybrids must be considered. The obvious candidate species for hybrid origin of U. calva Loew is U. lata Loew with a naked mesonotum and U. anatoliensis Gibbs sp. nov, with undusted occiput. However, U. calva has some unusual characters that suggest it cannot be derived from these two. The very narrow, linear oral margin and narrow, almost parallel-sided frons are closer to the males of these two species than females. No other known species seem likely to have produced the suite of characters present in U. calva . The most likely aberration that might produce such specimens is some form of gynandromorphy, females with male-like oral margin and frons. However, such specimens usually show undeveloped or vestigial genitalia which is not the case in the two species studied. Given the information currently available it is best to treat it as a good species.

Distribution. West Turkey. Although the lectotype location, Bosdagh, (also spelt Dosz-dagh in Lederer’s account) does not accord with any modern spelling, it is known that the collector, Julius Lederer, visited Izmir in 1864 ( Lederer 1866) so is very likely be Boz Dağlari near this city.

Figures

FIGURE 19. ♀ U. calva lectotype mesonotum.