Bull Thistle Gall Fly

"Urophora stylata" is a species of tephritid or fruit flies in the genus "Urophora" of the family Tephritidae. The host plant for the larvae is usually a thistle of genus "Cirsium" or "Carduus". It has been introduced in North America as a biocontrol of "C. vulgare", which has become an invasive species.