Public Works and Environmental Services
Department Resources
Related Resources
Caterpillar Look-alikes to Spongy Moth
The spongy moth is just one of many insects that feed on tree leaves. There are several caterpillars common to Fairfax County which are often mistaken for spongy moth. Each of these has definite identifying characteristics which are true to the species. No two insect species have the same characteristics. The information provided here will aid you in differentiating the spongy moth caterpillar from others.
Caterpillars are pale yellow, green, or brown with two rows of black spots down their backs. They are mainly hairless when young. Pale yellow or light brown hairs appear as they grow. They are 1 1/2-2 inches in length and covered in silky hairs when mature. Caterpillars emerge in late May and feed on a wide variety of hardwood tree species. They build webs at the tips of branches and feed inside them. The webs become noticeable by August, and although these may be considered unattractive, the late season feeding rarely causes lasting damage because the trees have already had plenty of time to store enough energy for the winter. This is a well-established native with many predators, parasitoids, and diseases to control them.
Caterpillars have pale bluish lines along the sides of a blackish body with a row of cream-colored keyhole-shaped spots down the middle of their backs. They are sparsely covered with white hair and reach two inches in length when mature. They feed in oaks and other broad-leaf trees in late March to early April. They do not make a tent or hang by silken threads, but leave silken threads along branches, often congregating in social masses while molting. This well-established native has many predators, parasitoids, and diseases to control it.
Photo By: William M. Ciesla, Forest Health Management International, Bugwood.org
Caterpillar is black and hairless with eight narrow yellow-orange stripes on its back. At maturity it is about two inches long and has a pair of long, curved ‘horns’ that point forward from its head. It is a common native of eastern North America that prefers oak leaves, especially red oaks. Defoliation becomes noticeable in August and September. Because it is a late-season defoliator with a host of well-established predators, parasitoids, and diseases to control it, it does not pose a serious threat to trees in Fairfax County.
