Nature News | Marlene A. Condon September 4, 2021
One October day in 1996, I attended an outdoors writers’ meeting in Warrenton. As I drove from Crozet early that morning, I saw hundreds, if not thousands, of Woolly Bear caterpillars on the roads. As fall begins, these furry reddish brown and black caterpillars become a familiar sight in Virginia.
You might spot Woolly Bears in summer feeding upon many kinds of wild flowers, grasses and trees. But most people notice their presence only when they see caterpillars crossing roads during September and October. Have you ever asked yourself “Why did the Woolly Bear cross the road?” It’s not “To get to the other side,” but rather “To find a good place to hibernate.”
As summer ends, many caterpillar species encase themselves in a protective covering and undergo internal changes to become adults, a process called pupation. Woolly Bears, however, spend the winter in larval form and do not pupate until spring. Therefore, they need to find a sheltered area where they will be hidden from predators and severe weather.
You might find Woolly Bears curled up under mulch or rocks in your garden, or in your basement if they found a way in. Once, when there was a threat of frost overnight, I covered some potted plants with “row cover,” a lightweight fabric used to protect plants from the cold. When I uncovered the pots the next morning, I discovered a Woolly Bear had apparently found the blanket to its liking and had spent the night curled up under it. It soon left to find a more permanent refuge.
The fall Woolly Bears are the second generation or brood of the summer. The first-generation caterpillars (the offspring of the moths that emerged from the caterpillars that had hibernated) pupated earlier in the season. After about two weeks, adults emerged, mated and laid eggs on the variety of plants Woolly Bear caterpillars feed upon until the coolness of fall prods them into finding shelter for the winter. Folks tend to notice them on the move.
The Woolly Bear is the immature form of the Isabella tiger moth that is active during summer nights. You might see one around an outdoor lamp or perhaps at the window of a lighted room. It is not a particularly eye-catching moth, with its two-inch orange-to-brownish-yellow wings that display faint markings. You probably wouldn’t pay much attention to it if you saw one.
Another name for this tiger moth caterpillar is the Banded Woolly Bear because it usually sports three bands of color: Two black ends and a middle section of reddish-brown. Folklore tells us that the greater the amount of black, the worse the coming winter is going to be, but instead, it’s an indication of a caterpillar’s age. Older caterpillars have less black and more reddish-brown.
The Woolly Bear is not as common a fall sight as it once was. Therefore, you might try to avoid running over this harbinger of winter, but only if it’s safe to do so.