The saddleback caterpillar

The saddleback caterpillar has stiff poisonous spines connected to poison glands on their bodies. Stings are rare and usually accidental.

Many caterpillars we see in the landscape today morph into beautiful butterflies such as zebra or pipevine swallowtails, causing minimal disturbance other than munching on our native flora.

From the Eastern tiger swallowtail to the great spangled fritillary, North Carolina hosts some impressive beauties. While most caterpillars are relatively harmless, there are some “stinging caterpillars” armed with poisonous hairs or spines on their bodies that may be seen throughout Western North Carolina.

Unlike bees, hornets and wasps, stinging caterpillars possess hollow quill-like hairs, called setae that are connected to poison sacs. When coming into contact, these hair or horn like structures break away, releasing toxins that may either penetrate the skin or spill out to spread on the surface area of the skin.

Now not all caterpillars with spines, barbs or bright colors are venomous. There is no hard and fast rule that distinguishes the stinging from the non-stinging caterpillars. The most common species of stinging caterpillars found in the Southeast belong in the family of slug caterpillars, flannel moths, giant silkworms, dagger moths, smoky moths and nymphalid butterflies.

Most recently a home owner brought into my office one of these little stinging critters known commonly as a saddleback caterpillar. This bright and spiny guy is the larvae stage of the slug moth (Acharia stimulea). Saddleback caterpillars grow to be about 1 inch in length and are dark brown with long brown horns with many spines. Bodies of saddleback caterpillars are distinguished by bright colored patterns of brown with crème or white margins and green markings that resembles a saddle on its back. They are most commonly found on oak, cherry and plum trees, but can be observed on dogwoods, blueberries, hydrangea and grapevines, too.

While this caterpillar is not a major horticultural pest, it has stiff poisonous spines connected to poison glands on their bodies. When a person comes in contact with these, the spines break and a venom is released Most reactions are little more than itching and burning pain but can vary from mild to severe, depending upon the area stung and the sensitivity of the victim. Stings from these caterpillars are relatively rare and usually caused by accidentally rubbing up against them while doing yard work.

If you notice one of these critters on your body or clothing, don’t hit it with your hand. Instead, take a stick and flick it off. The stinging hairs of these caterpillars can lodge not only in skin but also in clothing. Adhesive tape can be useful in removing hairs that are stuck in the skin. If you do get stung, wash the area with soap and water. Prompt application of an ice pack or baking soda may also 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.

Christine Bredenkamp is horticulture extension agent for Jackson and Swain counties.