One of our three fungus-feeding Cheilosia (characterised by bare eyes, long wings, partially pale legs and fused antennal pits), and readily separable from the other two by the orange-red 3rd antennal segment. Confusion is more likely with the smaller C. pagana, but in top view, the facial knob of soror is broad and hemispherical (pointed in pagana).

Although it may be possible to confirm records supported by good photographs showing the distinguishing features, it may be necessary to examine the specimen in detail.

Adults are usually encountered on umbellifer flowers.

May be encountered from June into early autumn.

A fungus feeder.

Widespread and locally frequent in chalk and limestone districts of southern Britain especially in calcareous grassland, scrub and woodland rides. Records extend thinly into northern England. It seems to be increasing.

Rare in Leicestershire and Rutland.

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