In the insect world, appearances can be deceiving. A cute, fuzzy, or brightly colored exterior may hide a painful surprise when handled carelessly. Caterpillars are the immature stages of butterflies and moths. Most of these are not intimidating, but some should be approached with caution.
Many caterpillars have bodies covered with pointed or barbed hairs for defense against predators. These hairs can produce irritation and rashes when they come in contact with human skin. Some species have hollow, stinging hairs with poison glands at the base. These special defensive hairs (called urticating setae) can puncture the skin and release venom. This venom produces a painful burning sensation and inflammation in many people.
Most stinging caterpillars belong to one of three groups: puss caterpillars, slug caterpillars, and giant silkworm moths. According to the USDA, most caterpillar stings in the South can be blamed on puss caterpillars. These insects are covered with dense brown hairs concealing shorter stinging setae. Some species even possess long wispy hairs protruding from the posterior, giving them a mouse-like appearance.
Slug caterpillars are varied in appearance with bodies bearing long fleshy lobes covered with brown hairs or colorful triangular projections. The saddle back caterpillar is the most common species, with its distinctive charcoal grey body and lime green saddle across its mid-section.
Puss moth caterpillars are sometimes called “toxic toupees” because they look like a mass of hair on a leaf. While they look soft and fluffy, these shouldn’t be touched as they can inflict extremely painful stings. The long fluffy hair often hides smaller sharp spines.
Not all giant silkworm moth caterpillars are dangerous to touch. But the larva of the Io moth is the largest stinging caterpillar commonly encountered in South Carolina. Mature larvae can reach lengths of 2.5 inches. These caterpillars are lime-green in color with bright horn-like spines and four rows of stinging hairs.
Stinging caterpillars are generally not encountered in large numbers. Many are solitary feeders on a wide variety of smooth-leafed shrubs and trees, though the saddle back has been found associated with garden crops, including corn. These caterpillars have one or two generations per year and transform into plain brown moths.
The majority of caterpillar stings result from careless handling or brushing against trees and shrubs while mowing the lawn or doing other yard work. Since these insects are rarely encountered and occur in low numbers, no chemical control is needed. The best ways to prevent stings are education and avoidance. Admire that colorful or cute and fuzzy caterpillar from afar and walk away with a pleasant memory – not a burning irritation. If you do get stung, tape may be used to pull out any broken spines that may still be in your skin. Wash the affected area with warm soap and water and promptly apply an ice pack to prevent swelling and reduce pain.
Originally published 02/01