As feeding progresses and growth increases, the black and greenish colors become more evident. The wasp-like adults may also be observed on host trees. The abdomen has a conspicuous broad orange band and tapers sharply towards the rear. Males have yellowish antennae as well as an orange abdominal band, but the abdomen is cylindri- cal and rounded at the rear. In the fall, larvae spin tough, silken, brownish cocoons for protection and hibernation.
Adults emerge the following spring after wintering in litter beneath the tree.
Emergence of adults depends on their physiological condition and temperature and moisture conditions in the cocoon's environment. Under normal conditions this occurs in the early part of June and by July most adults have emerged. Each female can lay 20 to 200 eggs in slits cut in the bark of young twigs. The eggs and egg slits can be seen readily by the unaided eye. After about eight days the eggs hatch and larvae crawl back to the older twigs to feed.