Usia similis Paramonov, 1950

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 : 70-73

Usia similis Paramonov, 1950

( Figure 16 , Plate XIX)

Usia similis Paramonov, 1950: 369 .

Usia aenea: Engel, 1932: 67 Textfig. 22, misidentification.

Type material examined. Type locality Spain. The lectotype, designated by Zaitzev & Kandybina (1983), is in ZIS and it has not proved possible to visit or to borrow the specimen or obtain photographsduring this study. However, Paramonov’s description is quite adequate to be certain that the non-type material examined in the current study belongs to this taxon.

Other material examined. Spain, Puerto, Santa Maria [Cádiz July 1905], [leg.] Dusmet/ M.N.C.N., Madrid [♂♀] ( MNCN) ; Meigen/ 926, 40/ Usia atrata, Spanian / U. aenea Rossi , det. Becker [♂ in Meigen coll. MNHN ]; Punta, Paloma (pris Tarifa, Cadiz), 0.50m, 3 May 1970, [leg.] P. duMerle [1 pair in cop, 10♂ 9♀ in MNHN].

Etymology. from Latin similis meaning “similar”, presumably to aeneoides , which Paramonov described in the same work.

Diagnosis. A medium sized, robust blue-black species very similar to U. aeneoides Paramonov , endemic to Iberia. Although hairs on head, mesonotum short they are clearly evident, especially laterally, white to pale yellow. Oral margin narrow but wider than in U. aeneoides , occiput densely grey dusted, including depressed area behind vertex, frons relatively narrow, with longitudinal and diagonal grooves. Mesonotal cuticle with strong serrate punctures that give it a very rough appearance, few smooth shining areas away from paramedian vittae. Wings in most specimens with clear pattern of yellow base, brown mid-anterior patch and clear tip and trailing edge. Genitalia large and prominent, lateral horn-like projections of gonostylus usually readily seen and rule out all but U. aeneoides Paramonov . Furca with distinct step between ‘arms’ and apical part.

Redescription. Measurements. Body length. 4.4–4.8 mm. Wing length. 3.9–4.9 mm.

Male. Head. Mouth-margin shining black, narrow but quite evident, about as broad as palps at widest point, obsolete above where it meets the dusting of the frons. Frons narrow (although a little wider than in U. aeneoides ), a fifth to sixth head width, shining black, the frons longitudinally striated anteriorly between broad, dense white dust spots which occupy half the length of the frons. Between dust spots and ocellar area the cuticle is diagonally grooved. Frons narrowest at vertex where narrower than third antennal segment, widening slightly to mid-point where it widens more abruptly before resuming its original angle to the anterior of the frons. Lateral ocellus separated from eye margin by about the shortest diameter of that ocellus. Vestiture short, on ocellar area about as long as the distance between lateral ocelli (including ocelli), yellowish white. Occiput densely grey dusted including on triangular area behind vertex which is slightly less densely dusted. White hairs covering occiput similar to those on disc of mesonotum, a little shorter above, longer below. Antennae black, third antennal segment about 1.5x longer than the scape and pedicel together, relatively elongate, almost bare dorsally, no more than a few inconspicuous very short setae. Proboscis black, hairless, about as long as thorax; palps short, dark brown, clavate with pale hairs, the longest conspicuously shorter than the length of the palps. Thorax. Mesonotum and scutellum shining black (blue-black in some lights) with strong surface sculpture of stellate hair insertions. Wrinkles tending to become more transverse laterally and on the bare paramedian lines. Pronotum, dorsum of post pronotal lobe, adjacent part of mesonotum, notopleuron and end of thoracic suture grey dusted. Scutellum shining with shallow irregular transverse wrinkles. Mesonotal hairing yellowish white, about long as those on ocellar tubercle on disc, longer marginally, acrostichals in 4–5 irregular lines, as wide as the paramedian lines, laterally uniformly distributed, most directed towards middle of mesonotum (pale hairs on disc easily lost). Scutellum uniformly short haired, longest hairs on the margin about half the length of the scutellum. Pleurae black with a covering of dense grey dust except narrow anterodorsal margin of anepisternum which is shining black and undusted (very narrow in one specimen). Pronotum and posterodorsal corner of anepisternum with short yellowish white hairs. Wing. Wing membrane faintly brownish yellow tinged distally. Basal to the humeral cross-vein veins and membrane yellow contrasting with the brown infuscated costal cell, first basal cell, basal half of R1 (except extreme base which forms a narrow, clear ‘window’) and R2+3, vein m-cu and extreme base of discal cell. This forms a clear pattern, best appreciated with the naked eye, similar to that of U. aeneoides and U. aenea . Anal lobe slightly convex but clearly narrower than anal cell, r-m approximately at to a little before middle of discal cell. Haltere. Yellowish white, becoming slightly brown at base of stem. Legs. Entirely black to dark brown, the coxae grey dusted anteriorly and relatively long haired; femora with the longest pale posteroventral hairs barely longer than half the greatest depth of a femur, tibia and tarsi with a covering of minute yellow-brown setulae only. Abdomen. Shining black, with faint bluish reflections, cuticle with conspicuous hair insertions and transverse welts which give the tergites a rough texture, a little more dense on basal tergites. Tergites transversely impressed with base and apical margin reflexed to form an undulating, ridged profile. Disc of the tergites covered with very short, whitish hairs which do not or only just overlap each other. Laterally and on the down-curved margins (especially apically) the tergites are clothed with relatively longer, whitish hairs, as long as visible part of apical tergite (in normally set specimens). Sternites densely grey dusted, also with similar, whitish hairs along their posterior halves. Genitalia. Rather large, conspicuous, globular, as long as the four apical visible tergites, shining black with rough cuticle similar to that of mesonotum. Gonocoxite covered in short, dense, yellowish to golden hairs, including on the conspicuous ‘horns’ either side. Viewed caudally the lobes of the gonocoxite are widely separated, between them a hairless, concavity, the cuticle reddish brown, with the gonostyli and tip of epiphallus usually easily visible. Gonostylus ‘T’-shaped with an extra point externally, reddish brown, epiphallus with two flattened paddle-shaped lobes apically, reddish brown. Epandrium fairly long, evenly convex with short, yellowish white hairs.

Female. As male except as follows: conspicuously broader oral margin which does not disappear above, almost as wide as length of the pedicel. Frons more widely separated, about a quarter head width, diverging evenly (almost) from vertex to front. Hairs on mesonotum and scutellum rather shorter, especially on scutellum. Anepisternum with shining anterior margin tends to be a little wider. Genitalia. Tip of abdomen coming to a rounded point; apical tergites much less densely punctate. Apical sternite transverse, tumescent either side, ridged and falling away steeply proximally, triple point apically. Furca pigmented, the arms long and broad, attached to the apical part at a distinct step, lacks any pigmented vaginal plate.

Discussion. This very distinctive species is clearly a sibling species of U. aeneoides Paramonov which has closely similar male and female genitalia and much the same general appearance. Its relationship to other Usia species is less obvious, while it shares the same wing pattern with U. aenea (Rossi) , there is little else in common with this species.

Before Paramonov recognised this taxon in his 1950 revision, both U. similis and U. aeneoides were confused with U. aenea . Although Becker (1906b) recognised specimens which fit the description of U. aeneoides , he seems to have had a female only so did not give it a name, referring to it as U. aenea var. However, he appears to have completely overlooked U. similis despite examining a male specimen in the Meigen collection in Paris which he named U. aenea . It is possibly this error that misled Engel (1932) into illustrating the genitalia of U. similis under U. aenea .

Distribution. Endemic to Iberia where so far only known from Spain. Only 24 specimens seen during this study, 21 of them from a single date/locality, the other three from two dates. Known collection localities are along the Atlantic coast of Andalusia between Cadiz and Tarifa, most recently in 1970. Seems to be a rare and very local species.

Figures

FIGURE 16. ♀ U. similis (left) & U. aenea (right) frons dorsally.