Key to the world genera of the Bacchine and Melanostomine groups A. Postpronotum pilose (Fig. MND 64) or if postpronotum bare, then face and/or scutellum at least partially yellow................................................................................................... other Syrphidae - Postpronotum bare; face usually and scutellum entirely black................................................... 1 1. Abdomen elongate to oval, as broad as or broader than thorax.................................................. 4 - Abdomen petiolate, at its narrowest (usually 2nd tergum apex), distinctly narrower than thorax........................ 2 2. Arista pilose, with pili much longer than aristal width; abdomen slightly petiolate, with 2nd tergum narrowed apically and distinctly narrower than 3rd tergum and thorax; hind tibia modified....................................... Spazigaster - Arista bare or at most pubescent, with pili only as long as or slightly longer than basal diameter of arista; hind tibia unmodified .................................................................................................... 3 3. Face with distinct tubercle (Fig. MND 7); metathoracic pleuron bare; scutellum without ventral fringe (not Neotropical).................................................................................................... Baccha - Face without tubercle, straight or convex; metathoracic pleuron pilose; scutellum with ventral fringe (Neotropical only)............................................................................................... Leucopodella 4. Metacoxa bare posteriorly; mesocoxa bare posteriorly......................................................... 7 - Metacoxa with a tuft of pile at posteromedial apical angle (Fig. MND 77); mesocoxa pilose posteriorly................. 5 5. Metepisternum with several fine subappressed hairs; katepisternum with pile patches broadly separated posteriorly, joined anteriorly.................................................................................. Xanthandrus - Metepisternum bare; katepisternal pile patches broadly separated throughout...................................... 6 6. Metafemur swollen; antennal pits continuous (Afrotropical only)......................................... Pelloloma - Metafemur slender; antennal pits separated (Neotropical only)............................................ Talahua 7. Metasternum greatly reduced, with deep posterior incision laterally so that sclerotized portion consists of a median diamond-shaped area with narrow anterior and lateral strips (Fig. MND 70); face not produced below, with small tubercle; male legs slender, without bristles, pile tufts or modified hairs............................................. Melanostoma - Metasternum entire (cf. Fig. MND 71); face variable, almost straight with weak tubercle or moderately or strongly produced forward ventrally; male sometimes with legs modified, either broadened, or with special bristles, pile tufts or modified hairs .................................................................................................... 8 8. Face not greatly produced anteriorly; basoflagellomere oval or slightly elongate, never more than twice as long as broad... 11 - Face produced greatly anteriorly, usually extending well anterior to antennal base; antenna elongate, as long as or longer than face; basoflagellomere elongate, 4 or more times as long as broad............................................... 9 9. Eye pilose; basoflagellomere elongate, more than 5 times as long as broad; male dichoptic............ Pseudoplatycheirus - Eye bare; basoflagellomere shorter; male holoptic........................................................... 10 10. Eye normal; gena and ventral occiput small, not enlarged; anterior tentorial pit shallow; facial stripe narrow (Neotropical (Andes)).............................................................................. Tuberculanostoma - Eye reduced; gena and ventral occiput enlarged; anterior tentorial pit deep; facial stripe broad (Palaearctic (Pamirs))............................................................................................" Tuberculanostoma " 11. Male proleg usually modified, with protibia apically and probasitarsomere expanded, or profemur or protibia with specialized chaetotaxy (Holarctic & Neotropical (Andean))............................................................. 13 - Male legs simple (Neotropical or Afrotropical)............................................................. 12 12. Face with transverse grooves dorsally along tubercle; facial tubercle low dorsally, not distinct; antennal pits separated (Neotropical)................................................................................... Argentinomyia - Facial tubercle distinct dorsally, without grooves; antennal pits confluent (Afrotropical)...................... Afrostoma 13. Mesonotum smooth or with puncta finer and more widely scattered, not producing a distinct rugose appearance; legs partially pale.................................................................................. Platycheirus ... 15 - Mesonotum distinctly and finely rugose; rugose appearance due to large and closely set puncta, puncta set in irregular rows; legs black........................................................................................... 14 14. Arista bare, inserted near middle of basoflagellomere; face wider ventrally, with sides divergent ventrally; abdomen with pale maculae.................................................................................. Rohdendorfia - Arista pubescent, with short, appressed pile, inserted basally; face not distinctly wider ventrally, with sides approximately parallel; abdomen entirely black................................................................ Syrphocheilosia 15. Wing shorter than abdomen; abdomen broad or mostly red or black with 2 yellow maculae on 3rd tergum...... Pyrophaena - Wing longer than abdomen; abdomen narrow, not with such abdominal pattern.................................... 16 16. Male: Protibia apically and/or protarsus expanded, usually with specialized setae; profemur without specialized chaetotaxy........................................................................................ Platycheirus (s.s.) - Male: Protibia and protarsus simple...................................................................... 17 17. Male: Profemur posteriorly on at least apical 1/2 with row of stiff straight black setae, with apical-most (last) seta longer and with its apex strongly curved.................................................................. Pachysphyria - Male: Profemur without such specialized chaetotaxy......................................................... 18 18. Face produced ventrally, pollinose with distinct bare puncta; male protibia usually with long black bristles proteriorly (Holarctic and Andean).............................................................................. Carposcalis - Face not produced, without distinct bare puncta; male protibia without such specialized chaetotaxy (New Zealand only)................................................................................................ Eocheilosia

Published as part of Thompson, F. Christian & Skevington, Jeffrey H., 2014, Afrotropical flower flies (Diptera: Syrphidae). A new genus and species from Kenya, with a review of the melanostomine group of genera, pp. 97-114 in Zootaxa 3847 (1) on pages 102-103, DOI: 10.11646/zootaxa.3847.1.5, http://zenodo.org/record/4928795