There are about 25 species of stinging caterpillars. These insects have hollow hairs that contain a mild poison. The hairs release the irritating substance when people handle the caterpillars or accidently brush against them. Most of these caterpillars are capable of causing only a mild itching or skin rash. The caterpillar that causes one of the most severe reactions is the puss caterpillar, Megalopyge opercularis. It can cause intense itching, swelling, local numbness, nausea, and fever (especially in children). This caterpillar is widely distributed in the southeastern and south central states and feeds on a wide variety of deciduous trees and shrubs. During some years it increases to unusually large numbers. The saddleback caterpillar (Sibine stimulea), the io moth caterpillar (Automeris io )and the flannel moth caterpillar (Norape ovina are other caterpillars known for their stinging hairs.
Avoid handling hairy and spiny caterpillars. Spray shrubs and trees on which these caterpillars are found with an insecticide containing carbaryl (SEVIN®). Make sure your plant is listed on the product label. Contact a physician if a severe reaction begins to develop.