
© CHRISTIAN FISCHER/WIKICOMMONS
BAD HAIR SEASON Oak processionary caterpillars (one shown) show great style in marching formation but then there’s the noxious hair problem. (It’s not the long hairs you need to worry about, but near-invisible short ones.)
Threats to trees and health aside, oak processionary moth larvae have socially redeeming qualities. Of course the guy's wearing a full-body protective suit with face mask and goggles good and snug. He's about to confront a nest of little fluffy caterpillars.
Insect control can get surreal in the London area's springtime battle against the young of oak processionary moths (
Thaumetopoea processionea). The species, native to southern Europe, probably
hitchhiked into England as eggs on live oak trees in 2005, the U.K. forestry commission says.
Adults are just harmless mate-seeking machines in city-soot tones. But when a new generation's caterpillars finish their second molt into a sort of preteen stage,
their short barbed hairs (called setae) can prick an irritating, rash-causing protein into any overconfident fool who pokes them. Even people who'd never torment, or even touch, a caterpillar can suffer as stray hairs waft on spring breezes. (
More on that below.)
The caterpillars aren't much for house cleaning. The baggy silk nest a group spins itself high in several kinds of oak trees accumulates cast-off skins still hairy with the toxic protein.

© TERRENCE FITZGERALD
MARCH OF THE CATERPILLARS Caterpillars of pine processionary moths (relatives of the oak processionaries) demonstrate the classic single-file processions that give the group their common name.
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