Blog post Tara Roth, Ph.D.

Hands Off These Fuzzy Caterpillars

You may have noticed a large number of these fuzzy caterpillars crawling around your yard. These are the caterpillars of the tussock moth (Orgyia vetusta) which were first laid in early spring. They will emerge as adults between May and July. The caterpillars of this moth prefer to feed on oak leaves so you may notice large numbers of them hanging out under oak trees. The caterpillars are beginning to form into pupae which can be found alone or in huge clusters near their favorite food. Only the adult male tussock moths can fly; the females have no wings.

Tussock moths are often considered poisonous by many people but the truth is the hairs on their body are just very irritating. These irritating hairs are called urticating bristles and they can cause similar reactions in people as poison oak (a patchy, itchy rash). The bristles of the caterpillars fall off when they are handled and can spread to other parts of the body. Some people see the rash immediately whereas other people may only see it up to 24 hours after exposure. Children are more likely to develop a rash than adults, so we recommend that children are taught to leave fuzzy caterpillars alone. If you do notice a rash after handing, don’t despair! The rash will disappear in 24-48 hours and in the meantime, you can sooth the itching with calamine lotion or antihistamines.