Parageron lutescens ( Bezzi, 1925 )

Gibbs, David, 2023, A world review of the bee fly tribe Usiini (Diptera, Bombyliidae) - Part 3: Parageron Paramonov s. lat., European Journal of Taxonomy 863 (1), pp. 1-162 : 38-44

Parageron lutescens ( Bezzi, 1925)

Figs 1 , 35–36

Usia lutescens Bezzi, 1925: 180 .

Usia lutescens var. minor Efflatoun, 1945: 223 .

Etymology

‘Yellow-coloured’ from Latin ‘ lūteus ’.

Type material of Par. lutescens (not examined)

Holotype in ESEC, other types in EFC. Type locality: Egypt, Kerdacé ( Bezzi 1925).

Not seen. Photos of the draws show six specimens standing over lutescens , three of them with red labels, in ESEC. At the time the photo was taken the three specimens with red labels appeared to be in good condition so the holotype probably still exists. Seven more mounts in EFC, two with red labels.

Type material of Par. lutescens var. minor (not examined)

Holotype in ESEC. Not seen. Type locality: Egypt, Mallaha 1927 ( Efflatoun 1945). Photos of the draw in ESEC show two mounts, both with red labels, one of which is lost, just pin remaining, the other survives but condition cannot be assessed from the available photos.

Other material examined

GAMBIA • 1 ♀; “ W. Div., Yundum, 19 November 1993 J.C. Deeming ”; NHMUK .

NIGERIA • 1 ♂; “ Bauchi, Yankari Game Reserve 7-8 March 1981 ♂ Transitional zone, Woodland to Savanna (leg. R. Dransfield, NMW. Z 1981-125 )”; NHMUK • 1 ♂; “same data as for preceding”; NHMUK • 1 ♂; “ 29 March 1980 /WT4, 14/standing over lutescens Bezzi in J. Bowden Coll., BMNH(E) 2003-159”; NHMUK .

SENEGAL • 2 ♂♂, 2 ♀♀; “Mereto, Terres-Neuves, April 1976, G. Couturier leg./ Usia lutescens Bezzi det. J. Bowden 1982”; MNHN • 1 ♀; “ Forêt de Bandia 3 March 1976, G. Couturier leg./Piège coloré/ Usia lutescens Bezzi det. J. Bowden 1982”; MNHN .

Redescription

MEASUREMENTS. Body length: 3.3–4.7 mm. Wing length: 2.9–4.8 mm.

Male

A rather variable species, possibly a complex of sibling species (see section below). This description is based on Senegalese specimens that seem to closely agree with Efflatoun’s (1945) description of Bezzi’s type.

HEAD. Gena relatively broad, at level of proboscis wider than depth of postpedicel, broadening out slightly but noticeably on to frons, entirely yellow in ground colour with thin coating of silky white dust, a slightly shinier border to the oral opening below. Frons in dorsal view approximately equilateral but concave along eye margin, lacking erect hairs. Eyes confluent for a length about equal to the long axis of ocellar tubercle, about 10 facets. Ocellar tubercle dark blackish, thinly grey dusted, all ocelli in direct contact with the eyes; a narrow, acute yellow triangle in front of front ocelli. Very short, pale yellow proclinate hairs on ocellar tubercle no longer than diameter of an ocellus. Eye facets in the upper three fifths enlarged, at least twice the size of those in lower part, rather sharply demarcated. Occiput, darker yellow than frons, variably dark in ground colour around neck, thinly whitish dusted and covered with white hairs longer than length of scape and pedicel combined. Antennae with scape and pedicel yellow, a little darker than frons, postpedicel variably brownish to brown-yellow a little darker than pedicel, significantly longer than scape and pedicel together. The tip of this segment is remarkably variable, simply pointed or with a double point, the lower one sometimes spine-like; erect pale hairs very short and inconspicuous along dorsum of segments. Palps small and slender, not swollen apically, pale yellow with short yellowish hairs. Proboscis relatively short, shorter than tibia and basitarsus combined, yellow, labrum conspicuously swollen basally equal to twice width of pedicel, labium brownish often with labella darker blackish-brown, the basoventral membrane yellow.

THORAX. Yellow in ground colour, mesonotum with three variable black vittae, sometimes clearly separated by yellow dorsocentral lines, the paramedian vittae ending before reaching the scutellum, often these black vittae coalescing, reaching the scutellum and more or less obscured by whitish dust. On each side of the thorax are dust-free, velvety, roundish to elongate-oval black spots on the thoracic suture. Just behind the suture and above the wing base is an often obscure, roundish dark spot, occasionally coalescing with the dark antehumeral vittae. In more densely dusted individuals, three narrow, darker vittae can be apparent superimposed on the median black ground-colour vittae. Hairs of mesonotum very pale yellow, absent on paramedian vittae, otherwise evenly distributed, relatively short and uniform in length, longest about half the length of scutellum, anteriorly reclinate, in hind third proclinate. Scutellum yellow, very pale yellow hairs a little longer than on mesonotum. Pleura yellow in ground colour, katepisternum black ventrally, meron black postero-ventrally, anepisternum often with a slightly darker, brownish antero-ventral corner, all thinly white dusted. Pronotum and anepisternum with white hairs like those on notopleuron.

WING. Membrane with a very faint yellow tinge, the veins pale yellowish. Crossvein r-m between basal third and middle of the discal cell, a little to distinctly beyond m-cu. Anal lobe well developed with conspicuously convex margin, noticeably broader than anal cell.

HALTERE. Knob whitish, stem slightly darker yellowish, especially at base.

LEGS. Predominantly yellow except for apical tarsal segments which are variably browner. In darkest specimens hind femora mottled and spotted with brown. Claws yellow basally with black apical half. Legs covered with short white hairs, longest on the coxae and femora, very short and adpressed on tibia and tarsi.

ABDOMEN. Tergites predominantly yellow with paler creamy-yellow apical margins occupying about a third to half the length of each tergite, less on tergite one. Darker specimens can be variably brownish on base of tergites, all very thinly pale dusted. All tergites with mid-length pale hairs those on disc about half the length of respective tergite, laterally hairs longer. Sternites similar but mostly creamy-yellow, hairing as tergites.

GENITALIA. Entirely pale yellow, small but quite conspicuous, the epandrium rectangular, dusting and hairing similar to tergites.

Female

Generally paler than associated males, the dark mesonotal vittae and pleural patches more often redbrown rather than black. Eye facets uniformly small, frons at its narrowest wider than the length of the postpedicel, hind ocelli separated from eye margin by about 1.5 times the diameter of that ocellus. Frons broadening evenly anteriorly, front of frons rather protuberant, gena rather broader than in male. Hairing generally shorter than in male, most conspicuously so on abdomen. Eighth sternite yellow with broad apical emargination bounded by protrusions.

Remarks

Unfortunately, it was not possible to study the material examined by Efflatoun and no more recently collected specimens from Egypt have come to my notice. Photographs of the collection in the Entomological Society of Egypt (ESEC), Cairo, show six specimens, of which 2–3 have red “ type ” labels. There are a further seven specimens in EFC, of which two have red “ type ” labels. As far as can be ascertained from the photos available most of these specimens are in reasonable condition, although one of the types in the EFC collection is probably lost. Of the two specimens of var. minor in ESEC, one appears to have been destroyed. However, Efflatoun’s (1945) very full description and illustrations fit the paler examples from Senegal very closely so there can be little doubt that these are the same species. Also, specimens from the Gambia fit very closely with Efflatoun’s description and I treat these as conspecific.

Specimens from Nigeria and Kenya are more confusing. The Nigerian specimens include three males that can be identified as Par. lutescens with confidence as they hardly differ from the Senegalese specimens. However, two specimens differ sufficiently to make identification uncertain so these, together with four females from Kenya are discussed separately below.

Variation or potential sibling species ( Fig. 36 )

The following three forms are all known from a single sex and in two cases, single specimens. It is quite possible that they are merely extreme examples of intraspecific variation, but with such limited material it is as yet not possible to reach a conclusion.

Swollen proboscis form ( Fig. 36a–e )

Material examined

NIGERIA • 1 ♂; “ Transitional zone, Woodland to Savanna / Bauchi, Yankari Game Reserve 7-8 March 1981. R. Dransfield, NMW. Z 1981-125 /WT12, 14, 15, 16/ Usia lutescens Bezzi det. J. Bowden 1982”; NHMUK .

MEASUREMENTS. Body length: 4.6 mm. Wing length: 5.2 mm.

Remarks

This single male was collected in association with typical Par. lutescens males (however, label data suggests that four water trap samples have been bulked so it is not certain if all three specimens with the same data were collected at the same precise locality). It differs from typical Par. lutescens most obviously in the much more strongly swollen base of the labrum, broader than the femora and about twice as wide as the gena. Point of frons extended back to a very fine point such that eyes touching for only 6–8 facets. Thorax rather densely white dusted thus obscuring black vittae and pleural patches. The genitalia exhibit small differences, apex of gonocoxite coming to a blunt point (sharply pointed in typical Par. lutescens ), in lateral view lacking easily visible subapical process (a setose process visible in typical Par. lutescens ) epandrium more parallel sided (expanded apically in typical Par. lutescens ) and tip of epiphallus different.

Large pale yellow form ( Fig. 36f–g )

Material examined

NIGERIA • 1 ♀; “ Bauchi, Yankari Game Reserve 28 March 1980. R. Dransfield, NMW. Z 1981-125 / wt 5 (9)/ Usia lutescens Bezzi det. J. Bowden 1982”; NHMUK .

MEASUREMENTS. Wing length: 4.1 mm.

Remarks

This single female specimen was captured the day before a typical male (the label data of these two differ only in date and water trap code numbers so it is clear that these two are not directly associated but were flying at the same time and in approximately the same area). It differs from typical Par. lutescens in being very pallid yellow, the dark mesonotal vittae and pleural patches hardly visible, just vaguely darker reddish-yellow. Even the undusted spots on the thoracic suture are more brown than black. It is possible that this female is merely a teneral example, however, the proximal part of the genital fork also differs slightly. The form of the eighth sternite is so close to typical Par. lutescens as to be essentially identical.

Small pale yellow form

Material examined

KENYA • 4 ♀♀; “ Kora National Reserve , nr. S. bank of Tana River pitfall trap, July-August 1983, N.M. Collins & J.M. Ritchie / Usia (Parageron) lutescens Bezzi det. J. Bowden 1985/ NMW.Z.2007.035”; NHMUK .

MEASUREMENTS. Body length: 2.5–3.0 mm. Wing length: 2.7–3.0 mm.

Remarks

This small series of four female specimens from Kenya represent the most southerly examples of this genus known. They are superficially rather strikingly different from typical Par. lutescens being conspicuously smaller and very pale, washed-out yellow. The most important difference is the form of the proboscis, as long as head and thorax together it is conspicuously longer than in typical Par. lutescens . Additionally the labrum is only slightly swollen basally, about as wide as gena. Mesonotal vittae red-brown, only median one readily visible, antehumeral vittae very vague and pleura hardly darkened at all. The spots on the thoracic sutures reddish brown. The genitalia do not differ in any meaningful way from the ‘large pale yellow form’ described above and the eighth sternite is also closely similar.

Like the ‘large pale yellow form’, these specimens might be merely teneral specimens. However, the fact that all four are identical in colour and the form of the proboscis suggests that these specimens could be an undescribed species. Certainly, of the three forms described in this section, the ‘small pale yellow form’ is by far the most distinct. Given the apparent variability of Par. lutescens , it is safer to wait for male specimens to become available before this form is formally described.

Distribution

Gambia, Egypt, Nigeria, Senegal (and possibly Kenya).

Figures

Fig. 1. Parageron lutescens (Bezzi, 1925), ♂.

Fig. 35. Parageron lutescens (Bezzi, 1925), typical form. a. Epiphallic complex ventral. b. Epiphallic complex lateral. c. Gonocoxite ventral. d. Gonocoxite lateral. e. Epandrium dorsal. f. Female genitalia ventral. g. Female sternite 8 ventral.

Fig. 36. Parageron lutescens (Bezzi, 1925), Nigerian specimens. a–e. Swollen proboscis form. a. Epiphallic complex ventral. b. Epiphallic complex lateral. c. Gonocoxite ventral. d. Gonocoxite lateral. e. Epandrium dorsal. f–g. Large pale yellow form. f. Female genitalia ventral. g. Female sternite 8 ventral.