Every Spring, after all the canker worms have slid down their silk lifelines, they burrow into the ground, form a cocoon and wait until fall before they emerge again. This usually takes a couple weeks before they’ve completely gone away.
But they never really go away. They emerge in the fall, once the cold weather begins, as a moth. When they hatch these horny buggers breed. As is typical, the males fly away, leaving the wingless mothers crawl up the tree and lay their eggs. The eggs then lie in wait until next Spring, so they can annoy you again.
This is why tree banding is so important. If you can catch these moths as the crawl up a tree’s trunk, they won’t be able to lay their eggs. That means, next spring, there will be less inchworms dangling from trees, getting caught in your hair, and hiding under your shirt.