webworm

n. (Zool.) Any one of various species of moths whose gregarious larvae eat the leaves of trees, and construct a large web to which they retreat when not feeding. [ 1913 Webster ]

☞ The most destructive webworms belong to the family Bombycidae, as the fall webworm (Hyphantria textor), which feeds on various fruit and forest trees, and the common tent caterpillar, which feeds on various fruit trees (see Tent caterpillar, under Tent.) The grapevine webworm is the larva of a geometrid moth (see Vine inchworm, under Vine). [ 1913 Webster ]