The Fall Webworm is a moth native across North America whose caterpillars wrap leafy branch tips in loose silk during summer and fall. Feeding usually harms a tree’s appearance more than its survival.
Appearance
Appearance
Adults are white, sometimes with small black spots, and span about 1.4–1.7 in (3.5–4.2 cm) across the wings. Mature caterpillars are about 1–1.25 in (2.5–3.2 cm) long, with long pale hairs growing from rows of dark or orange bumps.
A mature spongy moth caterpillar has five pairs of blue bumps followed by six pairs of red bumps along its back. A fall webworm is usually paler, has long silky hairs from many small bumps, and feeds inside a web around branch tips.
Why they get mixed up · Both are hairy tree-feeding caterpillars that can strip leaves.
Eastern tent caterpillars build their silk tent in a branch fork and leave it to eat. Fall webworm caterpillars enclose leafy branch tips and feed inside the web.
Why they get mixed up · Both make conspicuous silk shelters on trees.
Where it lives
Typical habitats
shade trees
yards and parks
orchards
woodland edges
Range
Its North American range stretches across the continent from southern Canada to northern Mexico. It has also been introduced to Europe and Asia.
Preferred conditions
The caterpillars use many trees and shrubs, especially where leafy branch tips can be enclosed in silk.
Behavior
Diet
Caterpillars eat the leaves of more than 100 kinds of hardwood trees, including walnut, willow, maple, fruit trees, and sweetgum.
Activity
Adults fly at night. Caterpillars are most conspicuous in late summer and fall, although timing varies by region.
Social life
Young caterpillars feed together inside an expanding silk web around leaves and branch tips. Older caterpillars may leave the group and feed alone.
Overwintering
The species overwinters as a in a thin cocoon near the soil surface or in another sheltered crevice.
Life cycle
Breeding season
In northern U.S. areas there may be one generation a year, while populations farther south may have up to four.
Larva
Newly hatched caterpillars first scrape leaf surfaces inside a silk web, then eat whole leaves as they grow.
Caterpillar food plants
More than 100 hardwood species can serve as food plants for the caterpillars.