The gall fly Urophora solstitialis has a striking appearance with well-marked, banded wings, but there are other similar species and care is needed with identification.  The larvae gall Musk Thistle (Carduus nutans), part or all of the receptacle and achenes are transformed into a hard woody gall containing one or more chambers, each with a larva.

Adult Gall

Unless identified by a recognised expert, a photo is required and the specimen should be examined with a microscope. In the comments box, state the key or ID method used and describe the size and identifying characters. If adults are photographed a note of the plant they were using may be very informative.

Where Musk Thistle occurs.

Peak time for adults is June to September.

Records come mainly from the southern half of Britain.

Status in Leicestershire and Rutland not known.