Origin:
This is a native species in North America and occurs from eastern Canada south into the northeast U.S. and west to the Pacific Coast. It is much more common in the eastern half of the continent.
Biology:
This species is closely related to the Eastern and Western tent caterpillars but differs in that the larvae do NOT create tents for themselves. They do, however, spin large mats of webbing on the trunk and branches of the host tree and use these to rest or to molt. They also differ in that they overwinter as masses of larvae on the trunk, rather than as the egg masses. When mature they pupate in a strong silk cocoon on the trunk, branches, or on nearby objects. They feed commonly on such trees as aspen, birch, and basswood and occasionally on oak. They do not seem to feed on maple very often. This species is strongly subject to periodic outbreaks where high populations are present for 5 to 8 years and then at low levels for the next 5 to 10 years. The larvae routinely leave a tree and wander over everything nearby, spinning silk over everything as they go. They are mistakenly referred to as “armyworms” at this time. Egg masses on the trunk and branches overwinter, hatch in the spring, and larvae pupate in late spring and early summer.
Identification:
The larva is similar to Gypsy Moth but lacks the same pattern of colored spots on the dorsal surface. It will be over 1 inch long when mature and were it not for the nuisance value it would be a very beautiful larva. It has a bluish background color which is separated into several long rows of stripes with a thin red stripe along each side of the dorsal surface and orange stripes on the sides. On the top a row of white “keyhole” shaped spots is obvious. Tufts of long white hairs protrude from either side the length of the body. The adult moth is similar to others in the genus, with males smaller than females. Color ranges from yellow-orange to dark brown with a pair of darker stripes across each forewing, running from top to bottom.
Characteristicts Important to Control:
The use of chemical sprays is often necessary to kill the larvae, including both synthetic insecticides as well as natural materials such as Bacillus thuringiensis. Sprays should be directed onto the foliage where the larvae are feeding, preferably treating when larvae are first noticed and damage is minimal.
