Cochliomyia hominivorax, the New World screwworm fly, New World screwworm (NWS) or simply screwworm or screw-worm, is a species of parasitic blowfly whose larvae (maggots) feed on living tissue of warm-blooded animals. It is present in the New World tropics. Of the four species of Cochliomyia, only C. hominivorax is parasitic; a single parasitic species of Old World screwworm fly is placed in a different genus. Infestation of a live vertebrate animal by a maggot is scientifically termed myiasis. While the maggots of many fly species eat dead flesh, and may occasionally infest an old and putrid wound, screwworm maggots are unusual because they attack healthy tissue. This increases the chances of infection and the damaged tissue attracts more flies.