any of several social caterpillars (genus Malacosoma and especially M. americanum of the family Lasiocampidae) that form large silken webs on trees and may cause serious defoliation
tent caterpillar
noun(tent caterpillar)
a moth (Malacosoma disstria of the family Lasiocampidae) whose orange-marked larva is a tent caterpillar and a serious defoliator of deciduous trees