Dilophus obsoletus (Hardy, 1951)

Skartveit, John & Freidberg, Amnon, 2023, Revision of the genus Dilophus Meigen, 1803 (Diptera, Bibionidae) from the Afrotropical Ecozone, Zootaxa 5360 (3), pp. 301-354 : 323-325

Dilophus obsoletus (Hardy, 1951) (figs. 19–20, 101–108)

Philia obsoleta Hardy, 1951

Holotype (male): REPUBLIC OF SOUTH AFRICA, Natal, Drakensberge, Van Reenen. Label data: ́ Natal / van Reenen/ Drakensberg / Nov. 1926 », ́ S.Africa / R.E. Turner / Brit. Mus./ 1926-499.», ́ Holotype » (circular label with red edge), ́PHILIA/ obsoleta/ det. 1948 Hardy/ D.E. Hardy », ́BMNH (E) #/ 252978», ́NHMUK 014427898 (with barcode) ». Paratypes (including « allotype », female), 1 ♁ 5 ♀♀, same data as holotype . MALAWI: Zomba, ii. 1911, J.E.S. Old. Leg, 1 ♁.

Previous records: Malawi ( Hardy 1951a)., Democratic republic of Congo ( Hardy 1952b), Republic of South Africa ( Hardy 1951a, Hardy 1960b), Lesotho ( Hardy 1960b).

Material: LESOTHO, Qachas Nek, 1 ♁ ( MZLU). REPUBLIC OF SOUTH AFRICA, Orange Free State, Bethlehem, Avondrust , 24.–27. x. 1994, 2 ♁♁ 8 ♀♀ ( NMSA) , Free State, Harrismith , 10.–12. xi. 2009, 7 ♁♁ 5 ♀♀ ( NMSA) , Free State, Mooihoekkop , 14.–16. ix. 2009, 1 ♁ ( NMSA) , Free State, Gelutsdal farm, 9.–10. xi. 2009, 1 ♀ ( NMSA) , KwaZulu-Natal, Thendele , 1 ♁ 1 ♀ ( NMSA) , KwaZulu-Natal, Royal Natal National Park, 7.–11. iv. 1951, Brick / Rudebeck / Swedish South Africa Expedition 1950–51, 2 ♁♁ 1 ♀ ( MZLU) , Eastern Cape, 8 km N Fort Beaufort , 21. x. 1994, 1 ♀ ( MZLU) , Western Cape, 9 km ESE George, Kaaimansrivier , 13. x. 1994, 1 ♀ ( MZLU) , Western Cape, Wilderness National Park , 17 km SE George, 14. x. 1994, 1 ♀ ( MZLU) . ANGOLA, Tundavala 8–10 mi NW Sa. da Bandeira, 27.–29.iii.1972, B.M. Southern African Exp. 1972, 1 ♁ ( NHMUK)

Diagnosis: A medium-sized (4–5 mm) species, antenna flagellum robust with 8–9 close-set flagellomeres. The species is easily recognised by the vein CuA 1 ending well before the wing margin, in all other afrotropical species it extends to the wing margin or very nearly so.

Male (fig. 19) (N=4):

Total length 4.3–4.5 mm (N=3). Black, shiny with sparse, yellowish, rather long pile, legs dark reddish-brown.

Head (fig. 102): Length 0.77–0.87 mm (N=2), width 1.03 mm (N=1). Rostrum very short, extending not at all beyond antennal base. Antenna short and robust, flagellum 0.28–0.31 mm long, 0.08–0.09 mm wide (N=4), 8–9- segmented, flagellomeres close-set and transverse with short, dense setulae. Palp rather slender, no segment clearly thickened, last segment cylindrical, about 4* as long as wide. Complex eye with short, rather dense, pale interocular pile. Ocellar tubercle low and rounded. Occiput with sparse, short, pale setae. Underside sparsely covered by medium-length, pale hairs.

Thorax: Length 1.33–1.52 mm, width 0.88–0.95 mm (N=4). Humeri brown at sides, otherwise shiny black. Haltere stem yellowish-brown, knob brownish. Prothoracic spine comb with 10–12 rather short, sharp spines, mesothoracic comb with 12–14 short, blunt spines. Mesonotum with about 10 acrostichal setae forming an irregular row on each side, otherwise smooth and shiny. Scutellum with short, pale marginal setae.

Legs: coxae black, femorae, tibiae and tarsi dark reddish-brown, shiny. Fore tibia (fig. 103) with three-four rather close-set mesal spines in oblique row. Apical spine circlet with eight rather short and blunt spines. Mid tibia with fine setae only, no spinose setae. Tibiae and tarsi versy slender. Femorae and tibiae with long, pale pile. Measurments in mm (N=4 unless otherwise stated): fore femur length 0.73–0.80, width 0.23–0.28, fore tibia length 0.74–0.82, width 0.09–0.13, fore first tarsomere length 0.43–0.45 (N=2), fore second to fifth tarsomeres, mid femur 0.75–0.83, mid tibia 0.72–0.83, hind femur length 1.15–1.21, width 0.17–0.20, hind tibia length 1.13–1.18, width 0.11–0.12, hind first tarsomere length 0.30–0.43, width 0.07–0.08.

Wing (fig. 101): Length 3.5–3.9 mm (N=4), width 1.24–1.28 mm (N=3), length/width = 2.75–3.12 (N=3). Hyaline with fine microtrichia. Costa and R-veins yellowish, posterior veins colourless. Costa extends to one third distance between apices of R 4+5 and M 1, basally with a few, long hairs, otherwise with sparse, rather short setulae about as long as width of costa. Humeral vein absent. Subcosta faint, segments of is scarcely visible, running close to R. R 1 ends before reaching wing margin. Pterostigma invisible. Basal Radial sector about one third the length of crossvein R-M. R 4+5 rather straight. M basally clearly connected to CuA. Fork of M strongly asymmetrical, with M 1 diverging from M/M 2. M-CuA joins M at furcation. CuA-veins rather strong but entirely unpigmented. CuA 1 with a kink at junction with M-CuA, terminates well before wing margin. CuA 2 mostly straight, but with a short turn basad apically.

Abdomen: Length 2.1–2.4 mm (N=2), width 0.6 mm (N=1), black, shiny, with sparse, short, pale pile.

Terminalia: Hypopygium (figs. 104–105) width 0.35–0.40 mm (N=2), trapezoidal in outline. Gonostylus 0.16 mm long (N=1), straight, rather sharply pointed. Epandrium rectangular, apically nearly straight, sparsely clad with fine setae. Ventral indentation of gonocoxosternite broadly w-shaped.

Female (fig. 20) (N=4):

Total length 3.6–5.0 mm (N=4, the smaller measurements obviously affected but abdomen shrinking)

Head (fig. 107): Length 0.83–0.87 mm, width 0.58–0.68 mm (N=4). Black, shiny. Rostrum not extending in front of antennal bases. Antenna with scape and pedicel brownish-yellow, flagellum 0.33–0.38 mm long, 0.10 mm wide (N=3), dark brown, 8–9-segmented, more robust than in male. Palp brownish-black, no segments conspicuously thickened, last segment oval, about three times as long as wide. Complex eye about one half length of head, rather flat with very sparse and short interocular pile. Ocellar tubercle low and rounded. Head extends about one-half eye diameter in front of complex eye. Occiput with few, paler setae, frons sparsely covered by fine, pale, reclinate hairs, underside with few, pale hairs.

Thorax: Length 1.55–1.87 mm, width 0.83–1.01 mm (N=4). Mostly orange-yellow, shiny and almost entirely naked. Mesonotum with a broad, black median stripe which sometimes extends at the spine combs to cover all of the combs, broadly interrupted before scutellum, but hind part of scutellum is also blackish-brown. Lower half of meron brownish-black, pleura otherwise yellow. Haltere stem yellowish-brown, knob brown. Mesonotum with about 8 fine dorsocentral setae, otherwise naked.

Legs: coxae and femorae orange-yellow, tibia and tarsi brownish-black, fairly densely covered by pale pile. Fore tibia (fig. 108) more robust than in male, spines larger, mesally with 4 spines, apically with circlet of 8 spines. Mid tibia with 2–3 spinose setae apicodorsally and an apical circlet of spinose setae. Measurments in mm (N=4 unless otherwise stated): fore femur length 0.65–0.82, width 0.27–0.35, fore tibia length 0.73–0.92, width 0.12–0.15, fore first tarsomere length 0.47–0.55 (N=3), mid femur 0.80–0.85 (N=3), mid tibia 0.83–0.87 (N=3), hind femur length 1.12–1.27 (N=3), width 0.20–0.22 (N=3), hind tibia length 1.18–1.33 (N=3), width 0.13–0.15 (N=2), hind first tarsomere length 0.38–0.53 (N=3), width 0.07–0.10 (N=3).

Wing (fig. 106): Length 3.9–5.2 mm (N=3), width 1.26–1.81 mm (N=4), length/width = 2.72–2.89 (N=3), rather long and narrow, hyaline, microtrichia stronger than in male. Costa and R-veins brown, pterostigma distinctive, light brown. R s about half as loing as R-M, venation otherwise as in male.

Abdomen: Length 1.9–2.5 mm (N=4) brown, shiny, sparsely clad with fine, pale pile. Cerci rounded, pilose.

Distribution and ecology: The species is distributed from the Cape region in the south north to Malawi and Angola. None of the specimens carry any data as to altitude, but the localities are apparently mostly montane.

Flight period: The available specimens have been collected between September–November ( Table 2 ).

Discussion: All the specimens available have more or less torn or crumbled wings, whereas most specimens of other species have at least one intact wing. It is possible that the somewhat reduced wing venation found in this species, with thin radial veins and a shortened CuA 1 may make the wing more fragile than in other species.