hyphantria

from The Century Dictionary.

• noun A genus of bombycid moths, having wings like those of Spilosoma, from which it differs in the labial palpi, of which the second joint is very short, and the terminal joint almost rudimentary. H. cunea is a common species, which forms a web on forest- and shade-trees, in which the larvæ; live gregariously; they are known as fall web-worms.

from the GNU version of the Collaborative International Dictionary of English.

• noun A genus of moths whose larvae are called fall webworms.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun fall webworms