50 years ago, flesh-eating screwworms pushed scientists to mass produce flies

Excerpt from the June 2, 1973 issue of Science News

A close up photo of a screwworm on a red background.

Screwworms crawl into open wounds of warm-blooded animals, including humans, and gorge on living tissue. To wipe out the pests, researchers deploy sterilized screwworm flies to mate in infested areas, resulting in eggs that can’t hatch.

John Kucharski

June 2, 1973 cover of Science News

Fly factory planned for Mexico Science News, June 2, 1973

A ‘fly factory’ whose product is living flies — 300 million of them every week — is to be built in southern Mexico to help eradicate screwworms, a major livestock pest.… They feed on living host animals through open wounds or sores. The fly factory will raise millions of screwworm flies, sterilize them with radiation, and release them from low-flying aircraft to mate with native flies, producing eggs that will not hatch.


Mexico and the United States joined forces to finally purge North America of the screwworm scourge. The fly factory opened in 1976 and legions of sterilized screwworm flies were released in both countries, including along Mexico’s Isthmus of T­ehuantepec to obstruct northerly incursions. The eradication program was so successful that it spread to Panama.

By 2006, the United States, Mexico and Central America declared themselves rid of the pest. Though brief outbreaks still occur, such as in Florida in 2016, deploying sterile flies remains an effective remedy. The tactic has inspired more recent efforts to control mosquitoes and other harmful pests (SN: 11/23/18, SN: 8/5/16).

Nikk Ogasa is a staff writer who focuses on the physical sciences for Science News. He has a master's degree in geology from McGill University, and a master's degree in science communication from the University of California, Santa Cruz.

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