Woolly Bear Caterpillars

Can these furry little caterpillars really predict the weather?

September 28, 2011

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.


They eat mostly weeds, including dandelion, clover, and grasses, and generally will not harm your orna­mentals or vegetables.

In fall, woolly bears cross roads or paths searching for protected places to overwinter. In spring, they resume eating until pupating in a cocoon made from silk and their own hair. Adult moths emerge in two weeks.Woolly bears are the Dale Earnhardts of the caterpillar world, crawling at a neck-snapping .05 miles an hour, or about a mile a day.

The woolly bear is celebrated with a festival each October in Vermilion, Ohio. Folks in Banner Elk, North Carolina, celebrate the upcoming ski season with an annual Woolly Worm Festival and Race.

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