Bacchini, Bigot, 1883

Huo, Ke-Ke, Zhao, Le, Mengual, Ximo, Li, Gang, Liu, Xin, Zhao, Lian-Jun & Chen, Zhen-Ning, 2022, Biema Huo & Zhao gen. nov., a new flower fly genus (Diptera, Syrphidae) from China, European Journal of Taxonomy 852, pp. 98-116 : 110-111

Identification key to genera of the tribes Bacchini and Melanostomini in China

1. Abdomen slender, usually petiolate, with the second abdominal segment 2 narrower than the tergite 3 ............................................................................................................................................. 2

– Abdomen usually parallel-sided or oval ........................................................................................... 3

2. Abdomen elongate, strongly petiolate, with abdominal segments 2 and 3 obviously narrower than scutellum .............................. Baccha Fabricius, 1805 (There are three species distributed in China)

– Abdomen short, with abdominal segment 2 as wide as scutellum, segment 3 wider than scutellum. Arista plumose. Face black ...... Spazigaster Rondani, 1843 (Only one species distributed in China)

3. Metepisternum with subappressed fine pile. Katepisternum with upper and lower pile patches joined anteriorly, broadly separated posteriorly; hind coxa with a tuft of pile at posteromedial apical angle ......................................... Xanthandrus Verrall, 1901 (There are three species distributed in China)

– Metepisternum bare. Katepisternum with pile patches broadly separated thoroughly. Hind coxa without a tuft of pile at posteromedail angle .................................................................................... 4

4. The widest part of abdomen at the end of abdominal segment 4, postabdomen conspicuous more swollen to a large volume than other segments in male. Alula narrow, as wide as basal width of cell c ....................................... Biema Huo & Zhao gen. nov. (There are two species distributed in China)

– Postabdomen not swollen in male. Alular lobe broader than width of cell c ................................... 5

5. Metasternum greatly reduced, with deep posterior incision laterally so that sclerotized portion consists of median diamond-shaped area with narrow anterior and lateral strips. Face not produced below, with small facial tubercle. Male legs slender, without bristles, pile tufts or modified pile ..... ....................................... Melanostoma Schiner, 1860 (There are eight species distributed in China)

– Metasternum not reduced, posterior margin shallowly concave, without distinct incision. Face straight or with undeveloped facial tubercle, moderately or strongly produced forwards and/or ventrally below. Legs in male sometimes broadened and flattened, or with specialized bristles, pile tufts or modified pile ......................................................................................................................... 6

6. Frons, mesonotum and scutellum irregularly wrinkled by coarse punctations. Face widened downwards in male. Abdomen with patterns of light colour .............................................................. ............................................... Rohdendorfia Smirnov, 1924 (Only one species distributed in China)

– Body smooth, or with fine punctuations, but not wrinkled ............................................................... 7

7. Wing shorter than abdomen. Abdomen broadened, red in most part, or black with two enlarged yellow spots on tergite 3 ... Pyrophaena Schiner, 1860 (There are two species distributed in China)

– Wing longer than abdomen.Abdomen narrow, without spots as above. Legs sometimes with modified pile, pile tuft or bristles in male and flattened and broadened anterior tibiae and tarsi ...................... ...................... Platycheirus Le Peletier & Serville, 1828 (There are 25 species distributed in China)