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Ouch! Poisonous Packsaddle Caterpillars

Have you ever been stung by a packsaddle caterpillar? If so, it’s an experience you will never forget. A number of years ago, I had an unfortunate encounter with one while picking corn, and the memory of it still gives me nightmares.

Packsaddle caterpillars are bright green with a brownish-purple spot in the middle of its back. The spines are filled with venom. Joey Williamson, ©2019 HGIC, Clemson University

Packsaddle caterpillars are bright green with a brownish-purple spot in the middle of its back. The spines are filled with venom.Joey Williamson, ©2019 HGIC, Clemson University

A packsaddle caterpillar, also known as a saddleback, is the larval stage of a limacodid or slug moth (Acharia stimulea). This 1-inch long, bright green caterpillar has a brownish-purple spot in the middle of its back. It got its common name due to its similarity of saddle that is designed to hold or support loads on the backs of pack animals. Four large projections, called tubercules, are covered in numerous poisonous spines filled with venom. In addition, the caterpillar’s sides are covered with smaller spines that are also filled with venom.

This caterpillar is native and has a wide range throughout the eastern United States. Commonly dining on the leaves of corn, okra, apples, roses, oaks, and other deciduous trees, packsaddle caterpillars are most prevalent in the late summer and early fall.

When stung, the victim will experience intense, burning pain and possibly nausea that could last for several hours. A rash may develop and last for several days. If a person has a severe allergic reaction, the symptoms may be more intense and might require medical attention.

The spines can break off in the skin. One suggestion is to immediately use adhesive tape to remove as many of the poisonous spines as possible. Wash the area thoroughly with soap and water. Applying an ice pack or a baking soda poultice may also offer some relief.

When in the garden, wear a long sleeve shirt and pants along with gloves to prevent a surprise encounter with these stinging caterpillars. Do not attempt to handpick one of them off with your bare hands. Always wear heavy, leather gloves or a stick to remove them.

For more information on saddleback caterpillars see, HGIC 2482, Stinging Caterpillars.

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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