University of Maryland Extension

Stinging Caterpillars

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

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

Key Points

  • 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 not that commonly found 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.

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

puss caterpillar next to damaged leaf

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,

It is not necessary to control any of these caterpillars. They cause minimal damage to trees and shrubs.

Rev. 2020

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