by Ric Bessin, Extension Entomologist
University of Kentucky College of Agriculture
Most people know that bees, wasps, hornets and some ants can sting to defend themselves or their nests. Only a few people realize, usually from first hand experience, that handling some caterpillars can produce some painful results. Recognizing the few stinging caterpillar species may prevent irritating encounters.
Caterpillar stages of moths often have spines and barbed hooks. Generally, these are for show and are quite harmless. But there are a few Stinging caterpillars of various shapes, sizes and colors. Stinging caterpillars possess hollow quill-like hairs, connected to poison sacs, that are used as defensive weapons. When these hairs are touched they break through the skin releasing the poison. Reactions can range from a mild itching to the more severe pain, dermatitis, and even intestinal disturbances.
Giant Silkworm Caterpillars
Two members of this group possess poisonous spines. These are large leaf feeding caterpillars with numerous spines over the body.
The two-inch long Buck Moth caterpillar is brown to purplish-black with numerous yellow spots. The body is protected with branched reddish spines that may have red or black tips.
These can be quite common on oak or willow from spring to mid-summer. There is a single generation per year.
The Io Moth caterpillar is overall light green, but along each side there is a narrow reddish line bordered below by a white line. Grown caterpillars are two inches long and covered with branched, black-pointed green spines. They feed on a variety of plants including corn, roses, willow, linden, elm, oak, locust, apple, beech, ash, currant, and clover.
There are several species of slug-like caterpillars that have poisonous spines. Slug caterpillars are short and stocky and creep about on leaves in a slug-like manner. The head and legs are not visible. Typically, there is one generation per year with the grown larvae found in the late summer.
This one-inch Puss Caterpillar is covered with a dense woolly coat of soft brown hair, with tail-like hairs at the rear end. Beneath the hairs are numerous short poisonous spines that can cause severe irritation. They are often found feeding on various trees and shrubs, including elm, maple, hack berry, oak, sycamore and others. Young caterpillars often feed in groups. Sting severity increases with size of caterpillar. Puss caterpillar stings are often more severe than those of other caterpillars.
The Saddleback Caterpillar is brown in front and rear, green in the middle with a purple spot in the center of the green saddle. There are prominent horns on the front and rear. Stings by this insect can cause severe irritation. Saddlebacks are typically found on deciduous trees such as basswood, chestnut, cherry, oak, and plum, but occasionally they can be found on corn.
The pale yellow-green Euclea delphinii caterpillar has four dark patches of spines toward the rear and numerous spiny, yellow or red fleshy lobes. Grown caterpillars have a brown area on the back. It feeds on oak, beech, chestnut, willow, pear, bayberry, sour wood, wild cherry and other trees. It is less venomous than the saddleback caterpillar.
The Hag Moth caterpillar resembles a dried leaf. The caterpillar is brown with nine pairs of fleshy lobes, all with stinging hairs. It is found on lower branches of assorted trees and shrubs, including oak, chestnut, dogwood, sassafras and ash. The caterpillars are usually seen feeding on the lower surfaces of leaves.
Stinging Rose Caterpillar
The Stinging Rose Caterpillar is a yellow to red spiny caterpillar with black and blue stripes down the middle of its back and less distinct red, blue and black stripes along the side of the body. There are prominent spiny yellow horns on the front, rear and center of the body. They can be found feeding on bushes and low tree branches of redbud, oak, hickory, bayberry, wild cherry and sycamore.
How to Avoid Stings
Most encounters with stinging caterpillars result from accidently brushing against leaves on which they are feeding. The chances of running into these insects are relatively low, but occasionally one species may be very abundant. Also the more time spent in wooded areas, the greater the opportunity for contact. Most of these caterpillars are distinctly marked or brightly colored. This can allow you to see and avoid them. If you find one on yourself, don't brush it off or slap it with a bare hand. Use a stick or other object to remove it carefully. Hollow spines may break off in clothing or gloves.
First Aid for Stings
No really effective home first aid treatments for caterpillar stings are available. Adhesive tape or transparent tape may be used to pull out some of the broken spines in the sting area. Washing the area thoroughly with soap and water may help remove some of the irritating venom. Prompt application of an ice pack or baking soda may help to reduce pain and prevent swelling. Antihistaminic drugs, often administered for bee and wasp stings, are reportedly ineffective. See a physician if severe reactions occur. Very young, aged or persons in poor health are more likely to suffer severe reaction symptoms.
Where stinging caterpillars are numerous or present hazards to people, such as around residences, recreation areas or schools, infested shrubs and trees may be sprayed to eliminate or reduce the caterpillars. Use products containing Bacillus thuringiensis or carbaryl for control. Always read and follow label instructions.
CAUTION! Pesticide recommendations in this publication are registered for use in Kentucky, USA ONLY! The use of some products may not be legal in your state or country. Please check with your local county agent or regulatory official before using any pesticide mentioned in this publication.
Of course, ALWAYS READ AND FOLLOW LABEL DIRECTIONS FOR SAFE USE OF ANY PESTICIDE!