University of Maryland Extension

Stinging Caterpillars Found in Maryland

Author: 
Stanton Gill, Extension Specialist, Central Maryland Research and Education Center
White flannel moth caterpillars have stinging hairs

Introduction

Most people are used to the idea that wasps and bees can sting and rarely think about caterpillars which also sting. In the case of Lepidoptera (moths and butterflies), it is not the adult stage that causes the painful sting, but the larval stage. The pain inflicted on humans is not from an ovipositor (stinger) like a bee or wasp but rather through the hairs on the body of the caterpillar.


How Do Caterpillars Sting?

Stinging caterpillars bear specialized nettling or urticaceous setae or spines. These structures are hollow and contain toxins from poison-gland cells. The caterpillars use these hairs as defensive structures for protection against predators. The sting of the caterpillar inflicted on humans is not from a deliberate attack, but the result of casual contact with toxin-bearing setae or spines. When brushed against, these structures break away, releasing toxins. In some cases, broken setae may penetrate the skin. Sometimes the toxins spill out and spread on the surface of the skin causing inflammation.


Reactions to Stings

Reactions to caterpillars vary from person to person, but a sting is a sting. In some cases the contact causes itching or burning sensations. Some people develop dermatitis, a rash, lesions, pustules, inflammation, swelling, or numbness at or around the area of contact. In extreme cases a person can have a reaction with fever, nausea and intense pain. The type of reaction depends on the individual person’s susceptibility and on the species of caterpillar, degree of contact, and type of toxin. Reactions may be especially severe for individuals with allergies or sensitive skin. Some people may consider stinging caterpillars only a mild nuisance at best.

Find out about the stinging caterpillars found in Maryland

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