The Gypsy Moth caterpillar feeds on oaks, aspen, and a variety of other hardwoods. A heavy infestation can leave summer oaks completely stripped of foliage. Several consecutive years of such feeding can kill trees entirely. The Gypsy Moth ranks as one of the "100 of the World's Most Invasive Alien Species," according to the World Conservation Union. It was first introduced into the U.S. around 1870, and is now a major pest of the eastern states.
In spring, the larvae hatch from their winter egg masses and begin feeding on new leaves. Caterpillars feed primarily at night, but in a year of high Gypsy Moth populations, may continue feeding through the day as well. After 8 weeks of feeding and molting, the caterpillar pupates, usually on tree bark. Within one to two weeks, adults emerge and begin mating. The adult moths live only long enough to mate and lay eggs, and do not feed. The larvae develop within the eggs in the fall, but remain with their eggs for the winter months and emerge when buds start to open in spring.