Warble fly is a name given to the genus Hypoderma, large flies which are parasitic on cattle and deer. Other names include "heel flies", "bomb flies", and "gad flies", while their larvae are often called "cattle grubs" or "wolves." Common species of warble fly include Hypoderma lineatum (horse) and Hypoderma bovis (cattle).
Adult warble flies are large, hairy and bee-like; brown, orange or yellow in color.
They are found in all continents of the northern hemisphere, principally between 25 and 60 degrees latitude.
"Warblefly" is also the name of an English folk/rock/punk band.
When they re-emerge, the larvae cause many swellings ("warbles") under the skin, causing some harm to animals, but not as a general disease. It doesn't burrow into the flesh, but stays under the skin (hence, its scientific name Hypoderma). Nevertheless, when accidentally destroyed by pressure, the larvae can cause large purulent swellings.
From the subcutaneous swelling, the warble will puncture the skin when coming out of the bovine. From those numerous holes, the hide is rendered valueless.
Unlike Lucilia larvae, migrating grubs generally don't cause any damage in the meat, but growing animals may have a lower daily weight gain. Milk yields may also suffer, but in adult cows, the infestation is generally limited, due to immunisation following the first infestation, as a calf.
Warble fly has been eradicated in many countries, beginning from Denmark and Western Germany, in the 1960s. They have also been eradicated from the United Kingdom, as well as from Belgium. The method was the pour on application of a organophosphorus compound.