A small fly with distinctive black wing markings.

Associated with various willows and most likely to be encountered where willows are present.

Late spring and summer.

The larva lives in a gall of Pontania bridgmanii or Pontania proxima. The host larva is killed and emptied; the inquiline then feeds on the interior of the gall. The full grown larva leaves the gall and pupates in the soil.

Widespread but not well recorded in Britain.

Status in Leicestershire and Rutland not known.