Cochliomyia hominivorax

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) eat the 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 (Chrysomya bezziana). 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 damaged tissue also attracts more of these flies.

The New World screwworm fly was the first species upon which the sterile insect technique was tested and then applied in a natural environment, resulting in the control and systematic eradication of this species from the United States, Central America, and parts of the Caribbean beginning in the 1950s. By the early 2000s, it was considered eradicated from North America. However, in 2024 and 2025, the New World screwworm was once again detected in Mexico, leading to renewed efforts to prevent its re-emergence as a threat to agriculture. Meanwhile, the fly is still widespread in tropical and subtropical parts of the Caribbean and South America, so that animals imported from these areas to non-endemic regions must be inspected or treated to prevent the pest's reintroduction.