Species Spotlight: Banded Woolly Bear

Banded Wooly Bear caterpillar

The Banded Woolly Bear is the larval form of the Isabella Tiger Moth (Pyrrharctia isabella). Many larva of the Arctiid species of moths are called "woolly bears" because of the long, thick bristly hairs that cover their bodies.

This species of woolly bear is black on both ends typically with a thick, copper band around its middle. The larva emerges from its egg in the fall and will overwinter in caterpillar form. The Banded Woolly Bear caterpillar produces a cryoprotectant which allows it to survive being frozen solid. In the spring the larva will thaw and begin to pupate into its adult form, the Isabella Tiger moth. The moth can be dull yellow or orange with a few small, black dots scattered on the wings. The hindwings, visible when the wings are spread open, are pink with grey dots. The body is large and covered with yellowish or brownish fuzz. The first pair of legs will have a reddish-orange color on the segments closest to the body.

Isabella Tiger moth

Despite its spikey appearance, the woolly bear`s bristly hairs do not inject any venom or cause injury like some plants and animals do to defend against predators. The primary defense of the Banded Woolly Bear caterpillar is to roll up into a ball.

The caterpillar feeds on a variety of plants including asters, maples, birches, corn and herbaceous flowering plants. In North Carolina, the Banded Woolly Bear caterpillar can transform into a moth within months of hatching. However, in colder climates where the plant growing season is shorter, the caterpillar may feed for several summers before pupating, freezing and thawing each season. Some have gone through as many as 14 winters.

Farmers used the Banded Woolly Bear caterpillar, which is abundant in the fall, as a predictor of winter weather: a thick middle stripe indicated a mild winter whereas a thin middle stripe would mean a severe winter. There is a Woolly Worm festival held in Banner Elk, NC each fall to celebrate the coming winter. It is now known that the stripping and coloration varies with the age of the caterpillar and even among caterpillars within the same clutch of eggs.

Here is a short video clip about a close cousin of Banded Woolly Bear caterpillar, talking about its ability to freeze, from the Discovery Channel: http://www.discovery.com/tv-shows/frozen-planet/videos/woolly-bear-caterpillars/