The larva of a species of tiger moth (Pyrrharctia isabella), the woolly bear caterpillar is also known as a woolly worm. They average about 1 1⁄2 inches long, and are bristly, with black stripes at each end and a reddish brown stripe in the middle. They curl into a ball when touched.
Popular folklore claims that the length of the center stripe on a woolly bear predicts the upcoming winter weather. If the black stripes on each end are longer than the middle stripe, the winter will be harsh. A wide center stripe means the winter will be mild. The accuracy rate of the caterpillars, however, has been difficult for scientists to determine. Among a group of woolly bears, the stripes can vary greatly, making their forecast difficult to confirm. Perhaps, like TV weathermen, some caterpillars are correct and some are not.