Urophora quadrifasciata

The term ‘quadrifasciata’ in the Scientific Name refers to the dark, four-banded pattern in the wing.

The fly produces galls in Knapweed flowers; these are in each achene (not in the receptacle), causing it to become enlarged with woody or papery walls.  

Urophora jaceana and U cuspidata also gall knapweeds, but the gall includes the receptacle as well as achene 

Adult Gall

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Meadows and verges where Knapweed is present.

Usually encountered in summer.

Two generations a year. Overwintering generation emerges as adults from galls in the mature seedheads in the spring when new flower buds are beginning to form.

It seems to be quite widespread in the southern half of Britain.

Status in Leicestershire and Rutland not known.