Dilophus buxtoni ( Hardy, 1948 )

Skartveit, John & Freidberg, Amnon, 2023, Revision of the genus Dilophus Meigen, 1803 (Diptera, Bibionidae) from the Afrotropical Ecozone, Zootaxa 5360 (3), pp. 301-354 : 327-332

Dilophus buxtoni ( Hardy, 1948) (figs. 23, 116–118)

Philia buxtoni Hardy, 1948

Holotype (female): UGANDA, Ruwenzori , Nyamgasani Valley. Label data: ́UGANDA/ Ruwenzori Range / xii.1934 – i.1935 / B.M. E. Afr. Exp. », «Nyamgasani Valley/ 10,500–11,500 ft. / D.R. Buxton », « Holotype ♀ / Philia / buxtoni/ D.E. Hardy » (handwritten on pink label) , ́ Holotype » (circular label with red edge), ́ PHILIA / buxtoni/ det. 1948 Hardy/ D.E. Hardy», ́BMNH (E) #/ 252974», ́NHMUK 014427895 (with barcode)». The specimen is in good condition except that the wings were missing. One wing was recovered from the bottom of the drawer and is stored in a gelatin vial pinned next to the specimen.

Previous record: Uganda ( Hardy 1948).

Diagnosis: The species is known from a single female specimen, is, however, easily distinguishable from all other species except D. bicolor by its large size (about 7 mm). From the latter species in can be recognised by the brown legs, pronotal spine row with 14 spines, thorax dark brownish with spines not notably darker.

Male unknown.

Female (fig. 23): Body length 7.2 mm.

Head (fig. 117): Length 1.45 mm. Black, slightly longer than wide, a little over twice as long as complex eye. Extends about one half eye diameter beyond fore margin of of complex eye. Ocellar tubercle prominent. Occiput and frons with rather long and dense, greyish-yellow pile, ventrally with long setae, particularly in anterior part, about as long as head width. Complex eye with conspicuous, rather dense, shart, greyish interocular setae. Antenna with pedicel yellowish-brown, rather stout, cylindrical, flagellum 0.46 mm long, 0.17 mm wide, 9-segmented, flagellomeres strongly transverse with short, dense setulae. Labellum yellowish-brown. Palp short, black, terminal segment oval.

Thorax: Length 2.8 mm. Humeri yellowish-red, dorsally otherwise black and shiny, setae yellowish. Pronotal spine row with 14 rather close-set, long, erect, blunt spines, posterior row with approximately 20 short, regularly spaced spines. Dorsocentral setae fine, uniserial, dorsally otherwise bare, sides of mesonotum rather densely setose. Pleura faintly reddish. Haltere with yellowish-brown stem, black knob.

Legs: Fore coxa reddish-brown, mid- and hind coxa yellowish-brown, with medium-long, rather dense, brownish pile and scattered, stronger setae. All femora brownish-orange with black apices, tibiae and tarsi black, fore tibia faintly reddish. Fore tibia (fig. 118) with 4 erect, medium-long, blunt mesal spines in an obtuse row, apically with 8 blunt spines. Hind femur and tibia slightly thickened, all tarsi slender. Measurements (N=1): fore femur 1.26 mm long, 0.50 mm wide, fore tibia 1.33 mm long, 0.19 mm wide, first fore tarsomere 0.92 mm long, 0.15 mm wide, mid tibia 1.36 mm long, hind femur 2.23 mm long, 0.41 mm wide, hind tibia 2.38 mm long, 0.29 mm wide, first hind tarsomere 1.12 mm long, 0.17 mm wide.

Wing (fig. 116): Length about 6.0 mm (not 8 mm as stated by Hardy (1948)), width 2.25 mm, length/width= 2.67, yellowish-brown fumose, costal cell slightly darker. Anterior veins dark brown, posterior yellowish-brown, distinctive. Costa with very short setulae, shorter than width of vein, extends to half-way between apices of R 4+5 and M 1. Pterostigma oval, brown, distinctive. Humeral vein absent. Subcosta fine, brown, distinctive except apically, running rather close to R. R 1 fine, distinctive to wing margin. R-M about 3.5* as long as basal Radial Sector. R 4+5 gently curved. Fork of M asymmetrical with M 1 diverging from M/M 2, crossvein M-CuA joins M at furcation. CuA 1 with a kink at M-CuA, the cell enclosed by the fork of CuA nearly rhomb-shaped. CuA/CuA 2 rather strong. CuP brown, basally distinctive but vanishes well before wing margin, A 1 distinctive, bent. Posterior margin with fringe of rather long, pale setulae.

Abdomen: Length 4.0 mm, dorsally black, ventrally dark yellowish-brown with rather long, yellowish pile. Cerci rounded, brownish-red, notably paler than rest of abdomen.

Distribution and ecology: The single known specimen was collected at about 3000 m altitude in the Ruwenzori mountain range, Uganda.

Flight period: No exact collecting date was noted for the single specimen, but it was collected in December or January.