The webworm or fall webworm is actually a caterpillar, and are the larvae of small moths that complete several generations per year.
There are two primary varieties , the blackheaded and redheaded webworm, have light green coloration with numerous black spots. They are covered with long white to faint yellow hairs, have light green coloration and numerous black spots. They are common throughout North America. Webworms are generally discovered when their silken webs appear on trees late in the season . They encase foliage and smaller branches in their silken nests. They differ from tent caterpillars which make smaller nest in tree crotches.
Fall webworm larvae feed on multiple species of trees including fruit trees, nut trees and ornamentals. They devour leaves later in the season and are not as much of a problem in relation to crop loss, the nests however detract from any aesthetic appeal of the landscape and multiple generations over long summers does lead to significant defoliation.
They spin silken webs over plant terminals, then feed on leaves, buds, and blossoms within the webs. The caterpillars will remain within the webbing until food is depleted, at which time new webbing is generated to encase larger areas.
They overwinter in the pupal stage which can be found in the remains of old nests, under loose tree bark and leaf litter. The adults emerge from late Spring early Summer. The eggs are usually deposited in layers of 200 or more eggs on the undersides of leaves. The eggs hatch in 5 - 7 days and a small mass of caterpillars will encase single leaves with their webs skeletonizing the host foliage.