The caterpillars live in masses of hundreds or even thousands in huge, spreading silken sheets that cover yards of vegetation, particularly apple trees, both domestic apples and wild crab apples. Although the photograph shows a single caterpillar, it was isolated for its portrait; it is more typical to find masses of them packed together. The cocoons resemble the small wads of cotton wool known as "Q-Tips" sold in pharmacies or seen in doctors' offices. Usually this species can be described as fairly common in our area, but occasionally it can occur in devastating abundance, leaving all apple trees, both wild and cultivated, totally denuded of leaves over a wide area. This happened, for example, in 1994.