The larvae feed on young green leaves in the outer branches of wild cherry, apple, pear, and other fruit trees.
Many caterpillars take shelter in each nest.
They feed outside of their tents, stripping the leaves from the branches extending from the nest. By the end of spring that portion of the tree is bare, and by summer, wind and rain have broken down the tent. Extensive defoliation is hard on trees because it forces them to use their energy to produce new leaves. For tents that can be reached, just pull 'em out and step on the mass on the ground, or drop into a bucket of water with detergent in it. BTW, the caterpillars ARE good birdfood.