Usia pusilla Meigen, 1820

Gibbs, David, 2011, 2960, Zootaxa 2960, pp. 1-77 : 60-63

Usia pusilla Meigen, 1820

( Fig. 9 & 23, Plate XVII)

Usia pusilla Meigen, 1820: 229 .

Type material examined. HOLOTYPE: “Carpentras” = France, [round label] Meigen , [reverse], 928/40, Usia pusilla , coll. Meigen. [♂ in Meigen coll. in MNHN].

The specimen is pinned through the dorsum of the thorax with an orange-headed pin. Head, left-fore and left-hind legs missing. Otherwise in good condition, no mould.

Other material examined. France, Provence, Mt. De Lure, 1200m Oak & conifer forest 2 June 2000, leg. M.J. Ebejer [♀ in PCME]; (26 [Drome]) Mornans, Ferme de Fondoresse , 2 July 1980, [leg.] P. DuMerle [♀ in MNHN] . Spain, Torres de la Alameda (M) 31 May 2000 Malaise, leg. A. Bari [♂ in spirit PCMC-T] ; Andalusia, Cortija del Alcazar N36˚55'15" W4˚5'18" 990–1200m 4 June 2006, leg. D.J.Gibbs [2♂ in PCDG]; above Alcaucin N 36˚54'44" W4˚6'17" 800–1050m 7 June 2006, leg. D.J.Gibbs [♀ in PCDG]; above Capileira N 36˚57'44" W3˚20'37" 1837m 8 June 2006, leg. D.J.Gibbs [3♀ in PCDG]; W of Capilerilla N36˚56'21"W3˚20'26" 1480m 7 June 2008, leg. D.J.Gibbs [10♂ 5♀ in PCDG]; Roman Br. Fondales, N 36˚55'20"W3˚19'10" 920m 8 June 2008, leg. D.J.Gibbs [1♂ in PCDG]; above Portugos, N 36˚56'55"W3˚19'14" 1500m 9 June 2008, leg. D.J.Gibbs [4♂ 2♀ in PCDG] .

Etymology. The specific epithet derives from the Latin “ pusillus = very little”. Although this is not an especially small species, the holotype male is a small individual.

Diagnosis. A small black short-haired species confined to southwest Europe. Hind femora with short, adpressed hairs, marginal hairs of scutellum about half mid-length of scutellum, hairs on ocellar triangle short, about as long as distance between lateral ocelli. From the very similar U. susanae by wider mouth-margin (in respective sexes) and usually duller, more roughened and matt mesonotum. Male readily identified by shorter, more globular genitalia, gonocoxite more convex and gonostyli not recessed. Female genitalia and apical sternite variable, females sometimes not reliably identifiable, even with dissection (Plate XVII).

Redescription. Measurements. Body length. 2.3–5.8mm Wing length. 2.4–6.1mm.

Male. The following description refers to Spanish specimens, Where they differ from French specimens characters of latter are in parenthesis. Head. Frons about a fifth head width (wider, between fifth and quarter), at narrowest point about as wide as length of third antennal segment, rather matt with poorly defined narrow stripes of whitish dust on anterolateral corners. Frons widens towards front relatively evenly, with no more than a slight discontinuity of the eye margin medially (barely perceptible). Mouth margin narrow but quite visible, broader than tip of palp but almost absent below, wider than in U. susanae . Ocellar triangle equilateral (very slightly obtuse), lateral ocelli separated from the eye by their diameter or a little less. Longest hairs on ocellar tubercle short, about as long as distance between lateral ocelli and appreciably shorter than width of frons at vertex (even shorter). Occiput covered with grey dust, including area behind vertex which is slightly more shining, and relatively short black hairs, shorter above, longer below. Antennae black, relatively long, third segment elongate, about twice as long as scape and pedicel combined, straight dorsally, convex ventrally at base, blunt ended, a few short setae dorsally, especially just before sulcus. Proboscis black, naked, about as long as mesonotum and scutellum. Palps small, clavate, black with distinct apical setae. Thorax. Entirely black, mesonotum subshining, more or less dulled by shagreened surface sculpture (less pronounced, more shining) hair insertions often difficult to trace. Lightly pale dusted on pronotum, postpronotal lobe, notopleuron and above wing. Hairs short, on disc of mesonotum similar to that on vertex, acrostichals irregularly biserial, paramedian lines bare back to level of wing base, duller than midline, laterally hairs evenly distributed becoming longer on notopleuron. Scutellum subshining, dulled like mesonotum, disc largely bare, marginal hairs barely exceed half the length of the scutellum. Pleurae black, predominantly covered in grey dust, anepisternum often with a narrow shining strip along front margin, anepimeron with small central shining patch and katepisternum ventrally dust-free. Anepisternum with dark hairs similar to those on mesonotum in upper half and posterior margin. Wing. Clear to vaguely tinged brownish yellow, veins pale brown, decidedly more yellow basally. Anal lobe convex, as wide as anal cell. Haltere. Yellow-white knob, stem infuscated. Legs. Black, coxae dusted on anterior face, otherwise legs shining but with rough texture to cuticle, with very short, adpressed dark hairs, the longest on mid-femora anteroventrally, but even these barely exceed half width of tibia. Hairs shorter and denser on tibia. Abdomen. Black, compact with broad tergites, rough surface sculpture of stellate hair insertions, covered with relatively short dark hairs. Tergite 1 and 2 grey dusted laterally on reflexed margin. Sternites grey-dusted with black hairs along posterior margins. Genitalia. Fairly large but compact and not very elongated, rather globular, positioned under the tip of the abdomen. Epandrium oblong with broadly rounded apical projections that, in dry specimens, wrap around the cerci and tip of gonocoxite. Epandrium rather evenly covered with short, dark hairs, shining, undusted. gonocoxite with longer hairs, bilobed basally, convex in lateral view. Gonostyli placed apically, relatively simple, blunt tipped.

PLATE XVII. Usia pusilla Meigen, 1820 ; a epiphallic complex ventral, b epiphallic complex lateral, c gonocoxite ventral, d gonocoxite lateral, e epandrium dorsal, f female genitalia ventral ( France), g female genitalia ventral ( Spain), h female sternite 8 ventral ( Spain).

Female. Very similar to male, frons marginally wider diverging more evenly and dust spots a little more conspicuous. Mouth margin also a little broader and clearly broader than in susanae . Hairs generally slightly shorter, especially on tergites. Sternite eight broadest basally, quite clearly embossed in basal half. In dry specimens apical half with long fold where sclerite membranous, this often with covering of grey dust. When macerated this area shows as a triangular translucent apical patch, either side of which, in sclerotised area, are often round translucent patches (single dissected female from France simpler, like U. susanae ). Furca pointed (rounded).

Discussion. Rather variable with the few French specimens differing from Spanish specimens in frons width, and very slightly in the nature of surface sculpture, especially on mesonotum. Genitalia also differ slightly, especially in female, however, differences in male genitalia too small to consider separating them at this stage.

Forms a sibling pair with the sympatric U. susanae , the two often occurring together, even in the same flowers. Also probably has affinities with U. novakii and U. hyalipennis that have similar epiphallus.

Distribution. Southern France, Spain. Probably quite common in the southern part of its range but French specimens are very few. Can often be found in good numbers in Andalusia, frequenting blue Campanula , pink Convolvulus , various species of Linum and a range of other flowers. In the literature this species is recorded widely in North Africa and Europe east to Croatia (Evenhuis & Greathead 1999). While Portuguese records are likely to be this species (or U. susanae ), on current evidence all records from countries other than France, Spain and Portugal are probably misidentifications.