Since its accidental release in Massachusetts in 1869, this pest has defoliated millions of acres of trees in the East. A notorious hitchhiker (hence the name “gypsy”), it’s gradually moving westward, traveling to new regions as egg masses attached to vehicles. An Asian strain which feeds on an even wider range of plants than the European type has shown up in the Western United States.

Newly hatched caterpillars can disperse by hang gliding on silken strands. Eventually growing up to 2 inches long, they’re marked with rows of blue and red spots; tufts of fine hairs protrude from their sides. They feed in such numbers that their excrement rains upon the ground.