Usia putilla 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 : 42-45

Usia putilla Becker, 1906

( Figure 12 ; Plate IX)

Usia putilla Becker, 1906b: 215 , stat. rev.

Type material examined. LECTOTYPE here designated; France, putilla, Lyon, Coll. Winthem / putilla det. Becker/ Type / Usia angustifrons B., Dr E.O. Engel det. [♂ in NMW] . PARALECTOTYPES; putilla, Lyon, Coll. Winthem / putilla det. Becker/ Type / Usia angustifrons Beck., Dr E.O. Engel det. [♂ in NMW] ; 103 [on micropin]/ putilla, Lyon, Coll. Winthem / putilla det. Becker/ Type / Usia angustifrons B., Dr E.O. Engel det. [♀in NMW]; putilla, Lyon / putilla, Lyon, Coll. Winthem / putilla det. Becker/ Type / Usia angustifrons B., Dr E.O. Engel det. [♀ in NMW] .

Originally described from an unspecified number of specimens of both sexes from Winthem’s collection, Vienna. Four syntypes were found in NMW, the male in best condition selected as lectotype.

Other material examined. Spain, Chañe (Segovia) 18.v–3.vii 2000, T. Malaise [♂] (leg. J.F. Gómez) ( PCDG) . France, Cavaliea [sic. = Cavalaire, Var], June [19]06, Museum Paris, ex coll. Hesse [♀ MNHN].

Etymology. from Latin putus, meaning pure or clear, + illa, a diminutive suffix; perhaps referring to its shininess and small size.

Diagnosis. A small to very small shining black species, known only from a few specimens from France and Spain. Entirely black, vestiture fine, relatively sparse and silvery white, hairs erect or slightly inclined. Occiput shining, male frons narrow, eyes separated by less than distance across lateral ocelli, rear half of frons parallel, silvery dusting coalescing in front of anterior ocellus or, in females, dust spots separated. Acrostichal setulae proclinate in all specimens seen. Pleurae dusted apart from small shining dorsal and posterior margin on anepisternum in some individuals. Wings faintly yellow-grey tinged, distinctly yellow basally, veins yellow, becoming darker distally, anal lobe narrow but trailing edge clearly curved, more than half width of anal cell. Genitalia typical of group, differing only subtly from close congeners, most importantly in membranous apical margin of epandrium, which extends for more than half length of sclerite.

Redescription. Measurements. Body length. 3.4–4.5mm. Wing length. 2.7–3.4mm.

Male. Head. Mouth-margin very narrow, almost absent towards rear of oral opening, frons at narrowest point a little less than distance across lateral ocelli, equal to three times diameter of anterior ocellus, lateral ocellus separated from the eye margin by about its radius or less. Ocellar tubercle shining black, anterolateral silvery grey dust spots on frons extending back to narrowest part where they coalesce, a covering of fine pale setulae on anterior part of frons. Occiput shining black without any noticeable pollinosity except in the two vertical occipital tumescence but even here black ground colour not obscured. Hairing moderate length, on ocellar area about as long as width of vertex at narrowest point. Proboscis black, hairless, about as long as the head and thorax together; palps very short and thin, black to brown with short pale hairs apically; antennae black, third antennal segment longer than the scape and pedicel together, all segments shortly-haired above. Thorax. Mesonotum and scutellum shining black except for dorsum of post pronotal lobes, anteroventral corner of notopleuron and small areas above the wings. Shining between punctures, in some individuals these punctures rather stellate, bare paramedian lines relatively conspicuous and extending back to the mid point of the mesonotum, each a little broader than the acrostichal area which has 5–6 lines of proclinate hairs, most of hairs on disc of mesonotum also proclinate. Mesonotum covered with short white hairs, that on the disc no longer than distance between lateral ocelli, on scutellum about as long as vertex at level of lateral ocelli. Laterally hairing a little longer and denser, the hairs erect or inclined inwards. Pleurae black with a covering of grey dust sufficiently dense to obscure the black ground colour except for small shining patch along dorsal and posterior margin of anepisternum. Posterior half of anepisternum and pronotum with rather longer white hairs. Wing. Wing membrane clear, only faintly tinged yellowish-grey, becoming yellow basally, the veins also yellow basally becoming conspicuously darker brownish in the apical half. Anal lobe narrow, but with rounded margin, just a little narrower than anal cell ( France) to a little over half width of anal cell ( Spain, Figure 12 ), r-m a little before the middle of the discal cell. Haltere. Whitish yellow, slightly infuscated at base of stem. Legs. Entirely black, the coxae grey dusted as in pleurae; femora ventrally with mid-length, pale hairs, up to length of width of tibia, tibia and tarsi with a covering of short, white setulae, longer on tibia. Abdomen. Shining aeneous black, the disc of the tergites covered with short, whitish hairs issuing from transverse welts. Laterally and on the down-curved margins the tergites are clothed with rather longer, whitish hairs. Middle tergites with a shining, impunctate apical margin often with longitudinal grooves. Sternites grey dusted with whitish hairs confined to the posterior margin. Genitalia. Relatively large and conspicuous for this species group, few useful details visible in pinned specimens, shining black and covered in whitish hairs. Most useful character is the membranous apical ‘V’ notch of the epandrium which extends for more than half of the sclerite.

Female. As male except as follows: broader, though still very narrow, oral margin, and conspicuously wider frons, lateral ocellus separated the eye margin by about diameter of that ocellus. Posterior half of frons shining black, parallel sided, about four times diameter of anterior ocellus, as wide or wider than length of longest hairs on ocellar tubercle. Anterior half of frons widening, lateral margins each side covered in dense whitish dust obscuring ground colour, central two-thirds shining black or dark brown. Third antennal segment sometimes a little shorter. Anal lobe broader, margin more convex, as broad as anal cell. Abdomen conical tapering to rounded point.

Discussion. This small shining black species is clearly very closely allied to U. manca Loew , and could possibly be the end of a cline of this species. If specimens come to light between north Italy and central south France that show intermediate characters then U. putilla Becker might need synonymising under U. manca . However, in the absence of such specimens the differences, though small, are sufficient to retain it as a full species.

Engel (1932) treated this taxon as a subspecies of U. angustifrons Becker and he wrote that he could understand why Becker described it again under the name U. putilla . If Engel had the types of U. putilla in front of him then his decision is inexplicable, even without dissection these two species are abundantly distinct. Perhaps Engel did not have the U. putilla types available, in which case he might have worked from Becker’s description alone. Becker (1906b) did list some useless features in his key (e.g., colour of wing membrane and position of vein r-m), but the width of the frons and nature of occiput, accurately described by Becker, should have been sufficient to convince Engel he was dealing with a distinct taxon. In his description Engel (1932) mentioned several characters (entirely dusted lower frons and dusted occiput) that do not fit Becker’s description of U. putilla .

Distribution. A rare and little known species so far only known from the Rhone valley near Lyon, and the Mediterranean coast, southern France and a single specimen from central Spain.

Figures

FIGURE 12. ♂ U. putilla wing.