Question: What are those worms that strip my trees bare in the spring, then hang from single threads?

Answer: Those are cankerworms. They first became a problem in the late 1990s, but they have been frequent mid-spring visitors since. Usually you will see only one life cycle of them each spring. While they do strip the trees completely bare and, therefore, do considerable damage, the trees usually seem to bounce back. Apply B.t. biological worm spray to control them.