University of Maryland Extension

Stinging Caterpillars

Group of saddleback caterpillars on leaf
Saddleback caterpillars 
Photo: William A. Carothers, USDA Forest
Service, Bugwood.org

closeup of saddleback caterpillar
Saddleback caterpillar spines
Photo: Gerald J. Lenhard, Louisiana State University, Bugwood.org


Most of the caterpillars that are called stinging caterpillars don't sting like wasps or hornets do. They have hairs or spines that sometimes have a poison gland at the base. When touched, the hairs break off and the poison is injected, causing an inflammation of the skin and a burning sensation that may feel like a bee sting. The reaction can be more severe if the eyes, nose or mouth are affected. Stinging caterpillars are uncommon around home and yards. Most feed on native trees and shrubs in wooded areas.

The saddleback caterpillar is not fuzzy, but has a striking green saddlecloth on its back with a purplish brown saddle in the middle. It also has irritating spines.

puss caterpillar next to damaged leaf

The puss caterpillar (above) is about an 1 inch long, when fully grown, furry, and gray to reddish brown in color.

The Io moth caterpillar is about 2 1/2 inches long when fully grown. It is bright green with red and white stripes and four rows of short, stinging spines.

closeup of green Io caterpillar
Photo: Io Caterpillar Steven Katovitch, USDA
Forest Service, Bugwood.org

It is not necessary to control any of these caterpillars. The best prevention for stings is to teach children not to handle hairy or spiny caterpillar. The Golden Guide to butterflies and moths has very good color illustrations of many caterpillars, moths and butterflies.

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