Why the US Plans to Drop Millions of Flies From Planes

Hundreds of millions of flies dropping from planes in the sky might sound like a horrible nightmare, but experts say such a swarm could be the livestock industry's best defense against a flesh-eating threat heading toward the southwestern US border.

An outbreak of New World screwworms — the larval form of a type of fly that's known to nest in the wounds of warm-blooded animals and slowly eat them alive — has been spreading across Central America since early 2023. Cases have popped up in Panama, Costa Rica, Nicaragua, Honduras, Guatemala, Belize and El Salvador. Most Central American countries hadn't seen an outbreak in 20 years.

The fly reached southern Mexico in November, freaking out US agricultural industry officials and forcing the closure of several border-area cattle, horse and bison trading ports.

Fighting Flies With Flies

This isn't the first time the US has battled these invasive bugs. The nation mostly wiped out New World screwworm populations in the 1960s and 1970s by breeding sterilized males of the species and dropping them from planes to mate with wild, female flies.