Dilophus riftensis, Skartveit & Freidberg, 2023

Skartveit, John & Freidberg, Amnon, 2023, Revision of the genus Dilophus Meigen, 1803 (Diptera, Bibionidae) from the Afrotropical Ecozone, Zootaxa 5360 (3), pp. 301-354 : 311-312

Dilophus riftensis sp.n. ( Figs. 6–7 , 48–55 )

Dilophus cf. antipedalis Wiedemann, 1818 sensu Hardy, 1951: 79 .

Etymology: The species is named after the Rift Valley running through East Africa. The known localities are all within the Rift Zone.

Holotype (male): KENYA, Kakamega Forest, 1525m, 23. ix. 2005. Label data: ́KENYA 1525 m / Kakamega Forest / 0°13’N, 34°52’ E / 23.ix. 2005 /A. FREIDBERG» and « Dilophus riftensis sp.n. / HOLOTYPE ♁ / J.Skartveit des. 2022» (handwritten on pink label). ( TAU).

Paratypes: sama data as holotype, 7 ♁♁ ( TAU)

Previous records (as Dilophus antipedalis ): Kenya ( Hardy 1951a), Tanzania ( Hardy 1960a), Malawi ( Hardy 1951a).

Other material examined: KENYA, Kakamega Forest, 1525m, 23. ix. 2005, 2 ♀♀ ( TAU), Mau Summit, 25. ix. 2005, 1 ♀ ( TAU), Taita Hills , Vuria Peak 2200m, 19. ix. 2005, 8 ♁♁ 2 ♀♀ ( TAU), Mt. Elgon , 3500m, 31. x. 1983, 1 ♁ ( TAU), Mt. Elgon , 3800m, 25. xi. 1986, 1 ♁ 2 ♀♀ ( TAU), Mt. Kenya , alpine zone, 3600–3900m, on Lobelia elgonensis , 7♁♁ 2♀♀ ( NHMUK barcodes 014427874-882), Mt. Kenya , heath zone, 3200–3500m, F.W. Edwards leg.,, 7♁♁ 1♀ ( NHMUK barcodes 014427883-890), Aberdare Range, Mt. Kinangop 3600m, x.1934, F.W. Edwards leg., 1♁ 1 ♀ ( NHMUK barcodes 014427891-892) . TANZANIA, W. Usambara mts., Mazumbai, 1890m, 10. xi. 1990, 1 ♁ (microscope slide, ZMUB B 8135 ), Ngorongoro Rservation Gate , 1650m, 3. ix. 1992, 1 ♁ ( TAU), «Tanganyika», 2300–3500m, B. Cooper leg, 4 ♁♁ 1♀ ( NHMUK barcodes 010922016-020) . UGANDA, N. Bugisha , 12.i. 1930, H. Hargreaves leg., 13♁♁ 1♀ ( NHMUK barcodes 010922021-034) . MALAWI, Mt. Mlanje. 22.viii. 1913, S.A Neave leg. ( NHMUK barcode 014427893) .

Diagnosis: A medium-sized (3.0– 4.5 mm) species, flagellum cylindrical, 8-segmented, wing light brownish fumose in both sexes with dark brown pterostigma and brown posterior veins. Anterior (pronotal) thoracic spine row with 8 large spines. Male hypopygium rectangular, gonostylus apically expanded, epandrium with concave posterior border.

Male (fig. 6)

Total length 3.06–4.55 mm (N=15).

Head (fig. 49): Length 0.77–0.87 mm (N=11), width 0.89–1.00 mm (N=6). Black. Complex eye large, intraocular setae very short and sparse. Ocellar tubercle rather small. Rostrum not at all produced. Occiput with long, pale, procumbent setae. Underside with short, pale, bent setae. Antenna medium-length, flagellum 0.26–0.32 mm long, 0.06–0.08 mm wide (N=15), cylindrical, 8-segmented.

Thorax: Length 1.11–1.45 mm, width 0.68–0.81 mm (N=16). Shiny black. Pronotal spine row with 8 strong, sharp, erect spines. Mesonotal spine row with 12 short, blunt spines forming a continuous arch. Dorsocentral setae rather long, erect and pale, acrostichal area bare. Pleurae with very sparse setae. Scutellum with relatively long, procumbent, pale marginal setae. Haltere blackish-brown with brown stem.

Legs: Dark reddish brown. Protibia (fig. 50) mesally with 4 strong spines on oblique row. Apical circlet with 8 spines. Mid tibia without strong, spine-like setae. Hind femur moderately clavate, all tibiae slender. Spurs short, curved, black. Measurements (N=16 unless otherwise stated): fore femur 0.64–0.74 mm long, 0.21–0.26 mm wide, fore tibia 0.72–0.83 mm long, 0.09–0.11 mm wide, first fore tarsomere 0.40–0.52 mm long (N=12), mid femur 0.68–0.79 mm long (N=15), mid tibia 0.70–0.89 mm long, hind femur 1.00– 1.21 mm long, 0.15–0.21 mm wide, hind tibia 1.09–1.28 mm long, 0.10–0.16 mm wide, first hind tarsomere 0.40–0.47 mm long (N=15).

Wing (fig. 48): Length 3.13–3.88 mm, width 1.11–1.28 mm, length/width = 2.77–3.13 (N=16), light brownish fumose with rather strong microtrichia. Pterostigma brown, oblong and distinctive. R-veins and stem of M brown, posterior veins light brown and distinctive. Costa with rather long setules, extending to about 0.4* distance between apices of R 4+5 and M 1. Humeral vein absent. Subcosta long, light brown, fairly distinctive, running well clear of R. R 1 terminating a little outside middle of pterostigma. Basal R s very short, about 0.2* as long as R-M. M basally quite weak, connected to base of CuA. Fork of M strongly asymmetrical. M-Cu reaches M considerably before fork. Fork of CuA wide, CuA 1 with small kink at M-Cu. CuA 2 apically a little bent basad. CuP very indistinctive, A 1 basally quite distinctive.

Abdomen: black, very sparsely setose.

Terminalia: Hypopygium (figs. 51–52) 0.28–0.42 mm wide (N=14), outline nearly rectangular. Gonostylus with a distinctive ́head», apically blunt. Epandrium wide, trapezoidal, posterior border concave, sparsely clad with rather long setae. Ventral indentation of gonocoxosternite broadly W-shaped, of medium depth.

Female (fig. 7):

Total length 3.7–3.9 mm (N=3).

Head (fig. 54): Length 0.66–0.68 mm, width 0.50–0.57 mm (N=3). Brownish-black, shiny. Rather long and narrow, posterior margin of complex eye removed about one eye diameter from occiput. Ocellar tubercle rather small. Frons with short, reclinate setae. Complex eye rather prominent, antennal insertion more than 0.5 eye diameter anterior to complex eye. Antenna cylindrical, flagellum 0.25–0.29 mm long, 0.08–0.09 mm wide (N=3), 8-segmented. Temples with rather long, pale setae.

Thorax: Length 1.42–1.53 mm, width 0.72–0.77 mm (N=3), yellowish-red to brownish-black, in pale specimens a prominent, hourglass-shaped black marking on pronotum. Pale specimens have a more or less prominent, dark dorsal stripe, at least posteriorly. Shiny, sparsely pilose. Pronotal spine row of 8 strong, sharp, erect spines, mesonotal spine row of 12 short spines forming a continuous arch. Haltere dark brown.

Legs: Coxae yellow to reddish-brown, same colour as thoracic pleura. Femorae yellow, tibiae and tarsi brownish-black. Protibia (fig. 55) robust with 4 strong, sharp, somewhat protruding spines on oblique row. Apical circlet of 8 strong, somewhat spoon-shaped spines. Mid tibia with enlarged, spine-like setae, two before apex and some in apical circlet. Hind tibia and all tarsi slender. Measurements (N=3 unless otherwise stated): fore femur 0.62–0.70 mm long, 0.26–0.28 mm wide, fore tibia 0.72–0.77 mm long, 0.12–0.13 mm wide, first fore tarsomere 0.47–0.51 mm long (N=2), mid femur 0.71–0.83 mm long (N=2), mid tibia 0.71–0.87 mm long (N=2), hind femur 1.05–1.25 mm long, 0.19–0.23 mm wide, hind tibia 1.11–1.28 mm long, 0.13–0.15 mm wide, first hind tarsomere 0.47–0.57 mm long.

Wing (fig. 53): Length 3.88–4.10 mm (N=3), width 1.36–1.46 mm (N=2), length/width = 2.65–2.97 (N=2), light brownish fumose, pterostigma and venation as in male.

Abdomen: Dark reddish-brown, shiny. Last sternite laterally yellow. Cerci rounded, rather broad.

Distribution and ecology: The species appear to be widely distributed in the southern part of the Rift Valley. This apparently rather eurytopical species has been found at altitudes between 1525–3900m. It has been found in numbers on Lobelia elgonensis .

Flight period: The specimens have been collected between August and February ( Table 2 ).

Figures

FIGURES 5–10. 5. Dilophus baleensis sp.n., female, habitus. 6. Dilophus riftensis sp.n., male, habitus. 7. Dilophus riftensis sp.n., female, habitus. 8. Dilophus paucidens Hardy, 1962, male, habitus. 9. Dilophus malagasicus sp.n., male, habitus. 10. Dilophus malagasicus sp.n., female, habitus.

FIGURES 48–52. Dilophus riftensis sp.n. 48. Male, wing. 49. Male, head and thorax. 50. Male, fore tibia. 51. Male, terminalia, dorsal. 52. Male, terminalia, ventral.

FIGURES 53–55. Dilophus riftensis sp.n. 53. Female, wing. 54. Female, head and thorax. 55. Female, fore tibia.