The web-like masses you see in tree branches every spring are the handiwork of Eastern Tent Caterpillars. After overwintering as a little black blob of eggs, hundreds of hairy caterpillars hatch out and form a silky nest. Although common, the larvae are quite beautiful: black with white, orange, and yellow stripes plus pale blue blotches on the sides. Caterpillars must leave the nest daily to munch on tree leaves, but they return for protection from predators and the weather. In a few months, after reaching about 2½ inches long, the larvae venture away for good to spin a cocoon. Adult moths hatch out about 3 weeks later.