Late season caterpillars are out in full force. Many use camouflage or secretive behavior to avoid predators. In contrast, stinging caterpillars have brittle, hollow spines connected to venom glands. These spines easily penetrate and break off in the skin. Then, the irritating venom goes to work. Reactions to the chemicals vary from slight irritation to pustules, inflammation, and intense pain. Contact usually comes when a person accidentally brushes against a caterpillar that they did not see.
The saddleback or packsaddle caterpillar (Figure 1) is one of the most familiar stinging caterpillars. It has prominent horns on the front and rear. Its stings can cause severe irritation. Saddlebacks feed on deciduous trees such as basswood, chestnut, cherry, oak, and occasionally they can be found on corn.
Not all stingers provide a visual warning. For example, the hag moth caterpillar (Figure 2) resembles a dried leaf. The brown caterpillar has nine pairs of fleshy lobes, all with stinging hairs. It is usually found on lower branches of assorted trees and shrubs, including oak, chestnut, dogwood, sassafras, and ash.
The tiny spines may be lifted from the skin with pieces of masking tape applied to the site. Do not rub the area until they are removed. Wash the wound with soap and warm water. Place an ice pack or cold compress on the wound intermittently (15 minutes on and 15 minutes off). See a physician if there is a severe or persistent reaction to the toxin.
More information on stinging caterpillars found in Kentucky is available at www.ca.uky.edu/entomology/entfacts/ef003.asp .
By Lee Townsend, Extension Entomologist