Xenomyia, Malloch, 1921

Pont, Adrian C. & Werner, Doreen, 2003, A new species of Xenomyia Malloch, 1921 (Diptera: Muscidae) from South Africa, a probable natural antagonist of blackflies (Diptera: Simuliidae), African Invertebrates 44 (2), pp. 147-147 : 6-8

Relationships: There are 15 described species of Xenomyia ( Pont 1980) , of which six are known from South Africa: hirtibasis (Bigot, 1885) , natalensis Zielke, 1970 , patersoni Zielke, 1970 , perplexa Emden, 1951 , setulosa Zielke, 1970 , and stuckenbergi Zielke, 1970 . The new species differs from all of these in the male sex by the spine-like posteroventral setae on the fore femur ( Fig. 4 ), the dark cloud of microtrichiae on the wing ( Fig. 5 ), and the absence of ocellar setae. The following brief key will enable the South African species to be separated:

Key to Xenomyia species of Southern Africa

1. Ocellar setae absent ( Figs 1–2 ). Proboscis slender, elongate ( Fig. 3 ). Katepisternal setae 1+2. Mid femur without trace of ventral setae. Presutural intra-alar seta (inner posthumeral) present. ♂: fronto-orbital plates enlarged, completely suppressing frontal vitta, and covered with short dense setulae ( Figs 1 , 3 ). ♀: 1– 2 pairs of orbital setae, directed inwards and forwards ( Fig. 2 ) ......................... 2

– Ocellar setae present and well-developed. Proboscis short, stout, bulbous. Katepisternal setae 1+1 or 0+1. Mid femur with at least short posteroventral setae (rarely absent in ♀). Presutural intra-alar seta (inner posthumeral) absent. ♂: frons of normal structure, with frontal vitta well-developed and much broader than a fronto-orbital plate. ♀: 1 pair of reclinate orbital setae ..................................... 3

2 (1) 1 postpronotal seta, the entire lobe covered with short dense setulae. Hind femur without anteroventral setae. Lower calypter creamy. ♂: wing with a dark cloud formed by dense, elongated microtrichiae ( Fig. 5 ) ....................... osculata sp.n.

– 2 postpronotal setae, the lobe with the usual fine sparse setulae. Hind femur with 1 anteroventral seta. Lower calypter dirty yellow. ♂: wing clear ......................... patersoni Zielke

3 (1) Katepisternal setae 1+1. 2 pairs of presutural dorsocentral setae, though anterior pair may be short ................................................................................................ 4

– Katepisternal setae 0+1. Only 1 pair of presutural dorsocentral setae ............... 5

4 (3) Lower calypter yellow. Only 1 postpronotal seta. Fore tibia without posteroventral setae ......................................................................................... hirtibasis (Bigot)

– Lower calypter brown. 1 strong and 1 weak postpronotal setae. Fore tibia with 1–2 posteroventral setae ...................................................... stuckenbergi Zielke

5 (3) Anal vein (vein A 1) of normal length, reaching more than halfway from its base to wing-margin. Claws moderately elongate, equal to length of tarsomere 5 on all legs. Hind tibia with 1 anteroventral seta. ♀: mid femur with 1–2 posteroventral setae in basal half; hind femur with 1 posteroventral seta in basal half ............... setulosa Zielke

– Anal vein (vein A 1) very short, not reaching halfway from its base to wing-margin. Claws very elongate, on fore leg equal to length of tarsomeres 4+5 combined. Hind tibia without anteroventral setae, except for perplexa ♂ which has a row of such setae. ♀: mid and hind femora without posteroventral or anteroventral setae .................................................................................................................... 6

6 (5) ♂: hind tibia without anteroventral setae; fore tibia without a posteroventral seta; hind femur with rows of anteroventral and posteroventral setae ......................... natalensis Zielke

– ♂: hind tibia with a row of long anteroventral setae; fore tibia with a posteroventral seta; hind femur with a few posteroventral setae before tip, without anteroventrals ................................................................................................... perplexa Emden

Within the broader afrotropical context, there are five species with the unique ♂ head structure shown in Figs 1–3 : azurescens Emden, 1951 ( Uganda) , calyptrata Emden, 1951 ( Kenya, Uganda), edwardsi Emden, 1951 ( Kenya, Tanzania, Uganda), oxycera Emden, 1951 ( Ivory Coast, Nigeria, Uganda), and patersoni Zielke, 1970 ( South Africa). X. osculata will key to azurescens in Emden’s (1951) key, but differs most obviously by the yellow, brown-tipped palpi and the single postpronotal seta. X. patersoni , the only other South African species of this group, differs by having strong ocellar setae, dark brown palpi, 2 postpronotal setae, ♂ hind femur with an anteroventral seta, and ♂ wing clear.

Figures

Figs 3–5. Xenomyia osculata sp. n. ♂ (paratype). 3. Head, lateral view. 4. Fore femur, posterior view. 5. Wing.

Figs 1–2. Xenomyia osculata sp. n. (paratype). 1. ♂ frons, dorsal view. 2. ♀ frons, dorsal view.