Science: Screwworm Factory

Worst plague of Florida cattle is a large bluish fly called the screwworm. The adult female lays eggs on wounds or scratches! and the eggs hatch into maggots that literally eat the victim alive. Screwworm maggots can kill a full-grown steer in less than ten days. But last week, with the enthusiastic approval of cattlemen, planes were scattering millions of live screwworm flies over Florida rangelands.

Reason behind this unlikely procedure is the pest's fatal weakness: the female mates only once. If a female happens to mate with a sterile male, she will lay...

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