Woolly Bear Caterpillars

You know it’s fall in Wisconsin when you see fuzzy brown and black caterpillars crossing your lawn, driveway and even the roads. And while woolly bear caterpillars can’t predict the severity of our winters (sorry, it’s a myth…) they can teach us a little about how insects survive our cold climate.

Woolly bear caterpillars are the larva stage of the isabella tiger moth. (Look it up. They’re beautiful.) We love to pick them up because their hairs are harmless and it’s cute to see them roll up into a “C” shape and then gradually emerge to crawl all over our hands.

These larva are on their way to find their overwintering home. They typically choose spots under leaves or logs to settle in. Then, they freeze. Their heart stops beating and their organs freeze. But they don’t die because their cells contain a cryoprotectant - think of it as animal antifreeze.

Come spring, they’ll form a cocoon and then emerge about a month later as the isabella tiger moth. Pretty remarkable life cycle for a creature we don’t think twice about!

If you find one and are looking for a children’s book to pair with your caterpillar, check out The Secret Life of the Woolly Bear Caterpillar by Laurence Pringle.