There are several species of flannel caterpillars that may be encountered. The ones most commonly reported in Central and Eastern Kentucky are the black wave flannel moth caterpillar and the white flannel moth caterpillar. Both have painful stinging hairs if one brushes against them; one is marked with bright warning coloration, while the other is difficult to see due to camouflage.
There are others in the group that also possess stinging hairs, such as the very painful puss moth caterpillar. Unlike other stinging caterpillars, the venomous spines are hidden underneath longer silky hairs. The shorter venomous spines from these may cause a painful sting, swelling, and blistering that may last for days (personal experience).
White Flannel Moth
The mature white flannel moth caterpillar (Figure 1) can reach 1 1/4 inch in length. The yellow body is marked with a wide black stripe down the back that is bordered with red at each end. This is warning coloration alerting other animals to stay away. There are 11 pairs of raised yellow tuffs along this strip bearing short stinging hairs (setae), and there are smaller tuffs along each side of the body. The dark long silky hairs do not sting, but shorter needle like hairs at the base of the tuffs do. The larvae can be common leaf feeders on redbud, among other hosts.
Black Wave Flannel Caterpillar
Very similar in appearance to the puss moth caterpillar in their final larval stage, black wave flannel caterpillars (Figure 2) can be commonly found in younger stages that look somewhat different from mature larvae. The younger larvae bear long white wispy hairs while mature larvae have thick coats of long hairs. Both have short stinging hairs hidden underneath. Hair colors vary from reddish brown to almost white. They feed on a wide variety of hardwood plants and can be common in late summer. The sting of black wave flannel moth is usually not as severe as the puss caterpillar.
There are no really effective home first aid treatments for caterpillar stings available; however, these suggestions may help:
- 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.
Ric Bessin, Extension Entomologist