Usia florea (Fabricius, 1794)

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 : 58-61

Usia florea (Fabricius, 1794)

(Plate XV)

Voluccella florea Fabricius, 1794: 412 .

Usia cuprea Macquart, 1834: 383 .

Usia gagathea Bigot, 1892: 374 .

Type material of V. florea examined. LECTOTYPE here designated; Algeria or Tunisia, florea / Volucella / ZMUC 0 0 503993 [1♀in ZMUC in poor condition with head, much of thorax, right wing, and all legs but mid-right missing] ; PARALECTOTYPE; ZMUC 0 0 503994 [1 unsexed in ZMUC, only dorsum of thorax, scutellum and wings surviving].

Originally described from an unspecified number of specimens. Two syntypes found in ZMUC, both in poor condition. The specimen which has the abdomen largely intact, and so could be sexed, was selected as the lectotype.

Type material of U. cuprea examined. LECTOTYPE here designated; Italy, Museum Paris, Sicile, leg. A. Lefebvre, Macquart/ TYPE / Usia cuprea [1♂ in MNHN in good condition].

Originally described from an unspecified number of specimens. A single male found in MNHN was selected as lectotype.

Type material of Usia gagathea examined. HOLOTYPE; Algeria, Alger [ Algiers], Usia gagatea [sic.] ♂, n.sp. Inedit, Quincy Octobre 1886. J. Bigot, Dr. Seriziat [leg.]/ U. florea Fab. Det. Becker / U. gagathea Ex coll. Bigot. [1♂ in OUMNH].

Other material examined. Algeria, North Algeria, Hamman Rhira, May 1911, (Rothsch. & Hart.)/ Algeria (Hon. L.W. Rothschild & Dr E.J.O. Hartert) 1914-57 1♂ ; Algeria, Algiers, May 1908 (Hon. W. Rothschild) 1908- 242, 1♀ ( BMNH) ; La Calle, Museum Paris, Algérie, Coll. H. Lucas 78-49/ 1201. [blue label]/ U. claripennis, H. Lucas det. [2♂]; 1211/ Usia claripennis, Macqt. [♀]; L’Alma, 7 May 1893, Museum Paris, Algerie, P. Lesne 6-97 [♂♀] ; Museum Paris, Env. D’Alger, Bové 126-38/ 126, 38 [on reverse of round blue label]/ U. cuprea, H. Lucas det. [♀] ; Museum Paris, Algérie, coll. H. Lucas 78-49 [♀]; Ouled Messelem, May 1893 / Museum Paris, Algérie, P. Lesne 6-97 [♀] ( MNHN) ; France, Nyons, vi [♂] ( MNHN).

Etymology. florea from Latin meaning “of flowers”; cuprea from Latin meaning “copper”; gagathea from Greek γαγατεσ meaning coal as in coal black.

Diagnosis. A fairly large black, species from northern Algeria. All shining black without any obvious coloured reflections, vestiture mid-length, not a very hairy-looking species. Occiput shining and undusted on upper part, thinly grey dusted below, hairs on ocellar tubercle shorter than distance across frons at vertex, frons in front of anterior ocellus essentially glabrous. Mesonotal vestiture mid length, longest acrostichal setulae about as wide as this line of hairs. Scutellar hairs much the same as median mesonotal hairs, the marginal ones usually about half mid-scutellar length in females (but these can be few or even missing in rubbed specimens), much shorter in males. Anepisternum mostly shining, a narrow band of dusting along posterior margin. Genitalia fairly large, epandrium conspicuously wider than long, very open apically, the aedeagus usually clearly visible, its hooked tip protruding beyond apex of gonocoxite; furca largely unpigmented, membranous, a small but distinct vaginal plate present.

Redescription. Measurements. Body length. 6.5–9.0mm. Wing length. 6–8.7.0mm.

Male. Head. Mouth-margin fairly narrow, narrower than the tip of the palps at its broadest, almost disappearing below, shining black. Frons rather matt and wrinkled, grey dusting laterally on anterior half, the dust spots separated by an undusted area a little more than one third of the frons width at this point. Frons narrowest level with anterior ocellus, conspicuously wider than width across lateral ocelli, lateral ocellus separated from eye margin by about the diameter of that ocellus up to twice its diameter. Vestiture not very long, on ocellar area shorter than the frons is wide at this point, whitish to yellow-brown. Occiput shining black on a fairly wide strip behind upper eye margin, thinly dusted centrally and below. Antennae black, third segment longer than the scape and pedicel together, all segments with very short setae above. Proboscis black, hairless, shorter than head and thorax together; palps short, black to brown, clavate with pale hairs, the longest shorter than the length of the palps. Thorax. Mesonotum and scutellum shining black except for a very narrow area of light dusting along suture between post pronotal lobe and mesonotum and above the wings root. Smooth except for hair insertions, bare paramedian lines extending back behind the mid point of the mesonotum, each about as broad as the midline which has 5–6 lines of hairs. Hind part of mesonotum slightly wrinkled close to scutellum, scutellum shallowly, transversely wrinkled. Mesonotum and scutellum covered with mid-length pale yellowish-white hair, that on the disc of the mesonotum conspicuously shorter than narrowest width of frons (i.e. longer than in U. accola but shorter than U. atrata ), even shorter on hind part of mesonotum and scutellum. Pleurae black with a rather thin covering of grey dust except anepisternum, which is shining black, ventral part of katepisternum which is subshining. Posterior third of anepisternum and pronotum covered with rather longer yellowish white hairs. A few pale hairs on the middle of the katepisternum in some individuals. Wing. Wing membrane faintly yellow tinged becoming more yellow basally, the veins also yellow although conspicuously darker than the wing membrane, base of stem of R darker brown and base of costa blackish. Anal lobe as broad as anal cell, r-m before middle of discal cell. Haltere. Yellow, becoming brown at base of stem. Legs. Entirely black, the coxae grey dusted with pale yellow hairs externally; femora with rather long, pale hairs, those on the ventral surface of the hind tibia longer than depth of tibia but shorter than depth of femora; tibia and tarsi with a covering of minute brown setulae only. Abdomen. Shining black, the disc of the tergites covered with short, neat, whitish hairs. Laterally and on the down-curved margins the tergites are clothed with relatively longer, shaggier whitish yellow hairs (similar to U. maghrebensis Gibbs sp. nov.). Sternites also with similar long, paler whitish hairs. Genitalia. Very large, occupying about half the ventral surface of the abdomen, shining black or partially brown and covered in long, pale hairs similar to those on the lateral margins of the tergites, longest on the gonocoxite. In pinned specimens the very broad epandrium and the distinctive ‘hooked’ tip of the epiphallus can usually be seen. The single French specimen differs slightly in having the lateral corners of the epandrium somewhat elongated and squared off in lateral view. Gonostyli also differ in being deeper basally.

Female. As male except as follows: noticeably wider frons, the lateral ocellus separated from the eye margin by conspicuously more than the diameter of that ocellus. Oral margin a little boarder. Vestiture on ocellar area conspicuously shorter but the scutellum has longer marginal hairs up to half mid-scutellar length, sometimes inconspicuous. Abdomen conical tapering to a rounded point. Apical sternite characteristic, triangular with a longitudinal ridge, the tip with an apical point and lateral blunt angles.

Discussion. The two remaining types of U. florea are in poor condition and one so damaged that it cannot be sexed. The best preserved specimen is a female but careful examination of the underside of the tip of the abdomen reveals the characteristic last sternite allowing confident identification with non-type material.

The lectotype of U. cuprea Macquart is problematic because of the surprising collecting locality in Sicily. Usia are highly prone to endemicity, many with restricted ranges and only one, U. versicolor (Fabricius) , is known to occur in both Algeria and Sicily. If U. florea really does occur in both Algeria and Sicily then it should also be found in the intervening countries of Tunisia and perhaps even Malta, as is the case for U. versicolor . Further, extreme eastern Algeria and northern Tunisia is occupied by another, apparently parapatric, member of the florea - group, U. accola . If any member of the florea -group were to occur in Sicily, then it is U. accola that would be expected. The provenance of the French specimen is even more worrying, labelled simply “Nyons vi [June]” with no year or collector indicated. That there should be a population of this species in south-central France, but with no records at all from the Mediterranean coast of France, mainland Italy, Spain or Morocco, seems highly unlikely. For both these specimens an error in labelling seems to be a far more likely possibility, or perhaps vagrancy or accidental importation.

In his original description, Macquart (1834: 383) said that Mr Alexandre Lefebvre found several specimens [of U. cuprea ] in Sicily and that the species is perhaps a variety of U. aenea Rossi ( Macquart 1834: 383) . It is clear from the descriptions in this work that Macquart understood U. aenea to be a species with a dark shade across the wing and that his U. cuprea lacked this marking. But it is very surprising that he thought it might be a variety of U. aenea and must have overlooked the strikingly different genitalia if he really had the type of U. cuprea before him. The ten specimens in the Bigot collection at OUMNH listed in Evenhuis & Greathead (1999) as syntypes show no evidence of being such. There are no Macquart labels on them, just Bigot’s locality labels. When Macquart described the taxon in 1834, Bigot was just 16 years old and had not yet begun to build the collection that, in the 1850s, he sent to Macquart to describe. So it is extremely improbable that he should have Macquart types from this early period in his collection (A.C. Pont, pers. comm.).

The genitalia of the holotype of Usia gagathea Bigot differ in some details from other specimens of this species. The data label gives merely “ Alger ” for collecting locality. Bigot often seems to have removed original labels, replacing them with his own. There is only one label on this specimen giving location, collector and name all in Bigot’s hand so this clearly is not the label applied by the original collector, if there was one. It is possible then that the specimen came from elsewhere in Algeria, not Algiers itself, so might be form a different population than most other specimens. However, the small morphological differences are more likely to be individual variation.

Distribution. Algeria, ( Italy, Sicily? Based solely on the Lectotype male of U. cuprea possibly a labelling error), ( France, based on single specimen with limited data, reliability cannot be assessed). All specimens with date data are over 90 years old, none being seen from the inter-war period when numerous naturalists were still active in Algeria. The lack of recent records from Algeria is unsurprising, but there is reason to be concerned for the continued existence of this species. If it ever occurred naturally in Europe it must have been very local and rare and now probably extinct.