Slug caterpillars are the most morphologically diverse and oddest appearing group of caterpillars in North America. Despite their highly variable body plan, slug caterpillars may be readily recognized by an examination of their venter. Instead of paired abdominal prolegs, they have medial suckers on the first 7 abdominal segments, which lack both prolegs and crochets. Their heads are often hidden from view, retracted well into the thorax.
Many species have urticating spines, which in a few, can deliver a very painful sting.
They are broadly polyphagous but show a preference for smooth-leafed trees and shrubs.