To a throng of goats foraging in a remote expanse of Sanibel Island, Florida, the low whir of a plane flying overhead was perhaps the only warning of what was to come. As it passed, the specially modified plane dropped scores of parasitic New World screwworm flies through an elongated chute onto the herd.

Then the plane’s whir gave way to the swarm’s buzz. It was 1952, and the U.S. Department of Agriculture was conducting a series of field tests with male screwworm flies that had been sterilized with gamma radiation. The experiment’s aim was to get them to mate with their female counterparts, reduce the species’ ability to reproduce, and gradually shrink the population — and its screw-shaped larvae’s propensity to burrow into living mammals before swiftly killing their host — into oblivio

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