Some caterpillars live alone. In fact, they can’t stand the presence of other individuals of the same species. Others live in colonies. If the caterpillars are large in size such a colony can be quite a sight.
Buff-tip moth caterpillars reach a decent size. And if the conditions are right, they’ll spend all their life as a caterpillar in one huge colony. Quite a shock for any host plant (see photo below). If you’re focusing on feeding traces on a caterpillar quest you’ll definitely notice these.