Over all length 6 - 8mm. A black-bodied fly with a pale head and a white scutellum. The wings are white with a black-W on them.
Meadows, hedgerows and woodland edges. The female lays her eggs in the stems of Creeping Thistles Cirsium arvense, where they form characteristic galls in which the larvae develop.
Status and distribution
Restricted to the south and east of England, where it can be quite common. The galls are regularly seen on the reserve.
Best time to see
May to August.