Dilophus suberythraeus Edwards, 1915

Skartveit, John & Freidberg, Amnon, 2023, Revision of the genus Dilophus Meigen, 1803 (Diptera, Bibionidae) from the Afrotropical Ecozone, Zootaxa 5360 (3), pp. 301-354 : 325-327

Dilophus suberythraeus Edwards, 1915 (figs. 21–22, 109–115)

Type material (according to Edwards 1915: 62): Holotype (female) KENYA, Molo , Mau escarpment st. no. 19, 2420 m .. 8.xii. 1911 ( NHMUK), M. Alluaud & R. Jeannel leg ( NHMUK). Paratypes: same data as holotype, 2 ♁♁.

Further records mentioned in the original description: KENYA, Mt. Kenya, lower forests, St. no. 39, 2400 m., 3 males, 1 female ( NHMUK), Mt. Kenya , intermediate forests, St. no. 39, 2800–3200 m., 3 males ( NHMUK), TANZANIA, Kilimanjaro, alpine zone, St. no. 70, 2600–3200 m., 1 male ( NHMUK). The first author was unable to locate any of this material in NHMUK, however there were some specimens apparently from near the type locality, but collected after 1915.

Previous records: Kenya ( Edwards 1915, Hardy 1948), Tanzania ( Lindner 1958), Republic of South Africa (dubious? Hardy 1951a).

Material examined: KENYA, Molo Mtn. , 1220m, 25.xii. 1927, R.L. Wood leg., 2 ♁♁ 2♀♀ ( NHMUK) , Aberdare Range, Mt. Kinangop , cedar forest, 2440m, x.1934, F.W. Edwards leg, 2 ♁♁ 1♀ ( NHMUK) , Uplands , 15. xi. 1986, 2 ♁♁ ( TAU) , Mau, East Mau , 28. viii. 1983, 1 ♀ ( TAU) , 20 km E Kericho, 2200m, 20. iv. 1992, 1 ♀ ( TAU) . TANZANIA, West Usambara Mts. , 21. xi. 1990, 1 ♀ (in alcohol, ZMUB A 37513 ) .

Colouration was verified by checking photos of live specimens taken by the senior author at TANZANIA, Moshi, Marangu Hotel, 26. xii. 2008. No specimens were collected on this occasion.

Diagnosis: A medium-sized (3.5–5.5 mm) species, habitually somewhat similar to D. erythraeus , but easily separated from this species on account on the elongate mouthparts and the costa extending well beyond apex of R 4+5.

Male (fig. 21): Total length 3.5–4 mm.

Head (fig. 110): Black. Rostrum elongate, extending about 0.3*length of upper complex eye in front of eye margin, notably beyond antennal base. Antenna slightly clavate, flagellum 8- segmented, flagellomeres close-set and transverse with short, dense, dark setules. The pedicel is yellowish-brown, flagellum brownish-black Palp rather short, black. Complex eye with short but rather robust, brown interocular pile. Ocellar tubercle low and rounded. Occiput with fairly long, brownish setae. Underside sparsely covered by long, brownish hairs. Palp blackish-brown, rather short, last segment oval.

Thorax: Humeri brown at sides, otherwise shiny black. Haltere stem yellowish-brown, knob dark brownish. Prothoracic spine comb with 10 rather short, sharp spines, mesothoracic comb with short, blunt spines. Mesonotum with pale brownish acrostichal setae forming an irregular row on each side, otherwise smooth and shiny. Scutellum with short, pale marginal setae.

Legs: entirely black, shiny. Fore tibia (fig. 111) with four strong, sharp mesal spines in oblique row. Apical spine circlet with eight rather long, blunt spines. Mid tibia with fine setae only, no spinose setae. Hind femur clavate, tibiae and tarsi slender. Femorae and tibiae with long, pale pile, the longest ventral setae on hind femur about one third the length of femur.

Wing (fig. 109): Costal cell brownish-yellow, membrane otherwise hyaline with fine microtrichia. Costa and R-veins dark brown, posterior veins brownish-yellow. Costa extends to one third distance between apices of R 4+5 and M 1, with quite long, sparse setulae about four–five times as long as width of costa. Humeral vein present, fine and oblique. Subcosta yellowish-brown, distinctive except apically, running well separated from R. R 1 distinctive to margin. Pterostigma oval, dark brown, distinctive. Basal Radial sector about one third the length of crossvein R-M. R 4+5 rather straight. M basally barely connected to CuA. Fork of M strongly asymmetrical, with M 1 diverging from M/M 2. M-CuA joins M long before furcation, segment of M between M-CuA and furcation about half length of MCuA. CuA/CuA 2 rather strong, CuA 1 about as thick as M. CuA 1 with a kink at junction with M-CuA, extends to wing margin. CuA 2 straight. CuP distinctive but does not reach wing margin. Posterior margin of wing with fringe of rather long setulae.

Abdomen: Black, shiny, with greyish pile.

Terminalia ( Fig. 112 ): Hypopygium oval, epandrium apically straight. Gonostylus straight, relatively slender, apically rounded and slightly expanded. Ventral indentation of gonocoxosternite W-shaped, relatively narrow.

Female (fig. 22): Total length 5.5 mm (N=1).

Head (fig. 114): Length 0.93 mm, width 0.57 mm. Black. Head extends about 0.75 eye diameter distally from fore margin of complex eye. Ocellar tubercle rather low and indistinctive. Frons with fairly coarse, pale, reclinate setae. Occiput with coarse but not particularly long, pale setae. Complex eye bare, a little protruding. Antenna with flagellum 0.38 mm long, 0.08 mm wide, yellowish-brown, cylindrical, 9-segmented with short setae. Palp yellowish-brown, robust, last segment cylindrical. Mouthparts telescopical.

Thorax: Length 1.53 mm, width 1.00 mm. Reddish-orange with a black dorsal stripe which covers the spine combs and the dosocentral area, a little fainter posteriorly towards scutellum. Proonotal spine row with 10 strong, sharp, erect spines, mesonotal spine row with 14 short, sharp spines. Mesonotum dorsally with a few, short and irregular, dorsocentral setae. Mesonotum laterally with about 20 short, fine setae. Pleura bare and shiny, reddish except for lower edge of meron and posterior part, whih are brown. Haltere yellowish.

Legs: Coxae and femora reddish-orange, tibiae and tarsi black, with short, pale setae. Fore tibia (fig. 115) robust, with four strong, erect mesal spines forming a transverse arch, apically with 8 strong, diverging spines. No spinose setae on mid tibia. Hind femur clavate, a little curved, mid- and hind tibiae and tarsi slender. Tibial spurs short, curved, sharp. Measurements (N=1): fore femur 0.57 mm long, 0.28 mm wide, fore tibia 0.72 mm long, 0.10 mm wide, first fore tarsomere 0.48 mm long, 0.08 mm wide, mid tibia 0.83 mm long, hind femur 1.10 mm long, 0.17 mm wide, hind tibia 1.20 mm long, 0.13 mm wide, first hind tarsomere 0.52 mm long, 0.07 mm wide

Wing (fig. 113): Length 4.6 mm, width 1.5 mm, length/width = 3.1. Membrane hyaline with fine microtrichia. Anterior veins brown, posterior veins colourless. Costa with fine setulae, about as long as width of costa, extends to half-way between apices of R 4+5 and M 1. Humeral vein fine, straight. Subcosta colourless, indistinctive. Pterostigma dark brown, oval, distinctive. Crossvein R-M about 3 times as long as R s.Fork of M asymmetrical.

Abdomen: Length 3.8 mm, width 0.95 mm. Tergites brownish-black, sternites yellowish-brown with fine, pale pile..Terminalia: Cercus rounded, bi-coloured: basal half yellowish-brown, distal half brownish-black.

Distribution and ecology: The species appears to be distributed in Kenya and Tanzania, and has been found at altitudes between 1200–3200 m. Hardy (1951a: 94) listed a record from ́Banhoek Valley, Stellenbosch Div.», in the Cape region of South Africa. We have not seen any specimens collected further south than Tanzania and regard it as highly likely that this record refers to a deviant specimen of Dilophus capensis which, like D. suberythraeus , has conspicuosuly elongate mouthparts.

Flight period: The species has been collected between August–December, also in April ( Table 2 ).

Figures

FIGURES 109–112. Dilophus suberythraeus Edwards, 1915. 109. Male, wing. 110. Male, head and thorax. 111. Male, fore tibia. 112. Male, hypopygium, ventral. Redrawn from Hardy (1951) Fig. 10b.