from
The Collaborative International Dictionary of English v.0.48
Webworm \Web"worm`\, 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]
Note: 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]