Forest Tent Caterpillars (Malacosoma disstria Hubner) range throughout the United States and Canada. HOSTS: Broadleaved trees. Non-tenting caterpillars. In one generation young larvae appear when the leaves are beginning to unfold. They are nearly uniformly black being less than one-eight of an inch, and bear conspicuous hairs. Colonies stay together and move about in a file, following silk trails laid down by leaders. The caterpillars do not spin a tent; instead, they form a mat on the trunk or branch, and here they congregate when at rest or during molting periods. They also spin silk strings which act as parachutes, that they use to move up and down from the crowns of trees. Summer. Ludlow, MA. USA. Wild.