Warble fly

Warble fly, also cattle warble or heel fly, large, beelike fly of the family Hypodermatidae that deposits its eggs on the legs or feet of cattle. There the larvae (cattle grub) enter the skin and migrate within the body for several months. This produces a characteristic painful lump, or warble. At maturity, the cattle grub emerges and pupates wherever it drops. The warble fly is a pest in Europe and North America, causing economic losses due to damaged hides and meat.