WARBLE FLY

also called cattle grub>, or heel fly any of several species of insects included either in the bot fly family Oestridae or the family Hypodermatidae (order Diptera). The warble flies Hypoderma lineatum and H. bovis -large, heavy, and beelike-deposit their eggs on cattle legs. The larvae penetrate the skin, migrate through the body for several months, and produce a characteristic lump, or warble, on the animal's back. The warble contains a hole, which is used for breathing. When mature, the cattle grub emerges and drops to the ground to pupate and transform into an adult fly. The insect's breathing holes in the cowhide reduce the latter's commercial value. Another warble fly that causes economic losses of leather, meat, and milk is a reindeer pest (Oedemagena tarandi). The warble fly is widespread in Europe and North America. Control methods include the oral administration to cattle of an insecticide and manual removal of the larvae from the animals' backs.