Io moth caterpiller is striking

Q. I found a striking-looking caterpillar in my garage. It is lime green, about 2 inches long and has branching spines all over it. I didn’t touch it, I just put in a plastic container. If I bring it in, can you tell me what it is?

Doris from Canfield

A. I asked Doris to drop off this caterpillar for closer inspection. She’s right – this is a cool caterpillar. It has bright colorization and colored bands along the sides. It’ a good thing Doris didn’t touch it because this is a Io moth caterpillar (Automenis io). The caterpillar is covered with venomous spines that can deliver a painful sting when touched, similar to touching stinging nettle.

The caterpillar and moth can be found through the eastern U.S. and into Canada and Mexico. In the north there is only one generation per year. The caterpillars are not picky eaters; they can be found munching on various trees, shrubs and grasses. While stings to people are uncommon, they can be severe enough to require medical help. Like other moths and butterflies, it has an interesting life cycle.

The adult moth emerges in spring. The moths are very distinguished looking with eyelike patches on the hind wings. These markings are believed to be there to fool and deter predators. The moths do not feed – they don’t have working mouth parts. Their only purpose is to mate and lay eggs. They live only for a week or two, so they can accomplish this task.

After mating, the female moth lays eggs in groups of 20 to 30 on leaves and stems of host plants. The eggs hatch in eight to 11 days. The newly hatched larvae are the first instar (development phase) of the caterpillar. The Io caterpillar has five instars, the last one being the large green caterpillar Doris found in her landscape. Soon, these caterpillars will spin their cocoons and pupate. They will spend the winter in their cocoons and the adults will emerge next spring.

We kept the caterpillar you sent in. We added some leaves and twigs to the box it’s in and we’ll watch and see when it spins its cocoon. Of course, we’ll need to put it in a protected place outside for the winter to see what we get next spring.

For more information and pictures of this caterpillar and the moth, go to http://go.osu.edu/iomoth.

This week’s question is answered by David Sprague, an OSU Extension master gardener volunteer in Mahoning County at the Mahoning Plant and Pest Clinic. Call the clinic at 330-533-5538 to submit your questions. Regular clinic hours are 9 a.m. to noon Mondays and Thursdays.