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College of Food, Agricultural, and Environmental Sciences


Woolly Bear Winter Prediction Not Science, But Fun

October 21, 2002

COLUMBUS, Ohio - The exit of summer always ushers in Fall familiarities - apple cider, pumpkins, changing landscapes and the site of nature's most recognizable caterpillar: the woolly bear.

Cute, fuzzy and downright fun to watch it inch its way across a sidewalk, the harmless caterpillar has enjoyed being at the center of weather folklore. Like the groundhog's shadow, the woolly bear's 13 distinctive black and reddish-brown bands have become a rule of thumb in forecasting winter.

According to the Old Farmer's Almanac, the longer the middle brown band, the milder and shorter the coming winter; the shorter the brown band, the longer and more severe winter will be.

For decades, people have taken this folklore to heart, even holding festivals - like the Woolly Bear Festival in Vermilion, Ohio, and the Woolly Worm Festival in Banner Elk, N.C. - to honor the caterpillar's knack for predicting the weather. But the myth, says Ohio State University Extension entomologist Barbara Bloetscher, is nothing more than that and holds little, if any, scientific weight.

"Last year I found five woolly bears. Two had a short brown band, one was completely brown and the other was indistinguishable. If you recall, Columbus had a really mild winter, so I've come to the conclusion that the woolly bear is just wrong," laughed Bloestcher. "It's a lot of fun, but I don't give it any credence."

The truth behind the woolly bear's band length actually has more to do with age than with predicting the weather. As the caterpillar prepares to overwinter, the caterpillar molts, becoming less black and more reddish-brown as it ages. Woolly bears overwinter from September to May, and are commonly found along nature trails and wooded edges and crossing sidewalks and roadways seeking overwintering sites.

"The length of the bands have nothing to do with the severity of winter," said Bloestcher. "Woolly bears hole themselves up somewhere for winter. What do they care what color they are?"

The woolly bear, also known as the woolly worm and the black-ended bear, is the larva of the Isabella tiger moth. The caterpillar falls under "bristled" species, of which there are several different colors: all black, all brown, yellow and gray. But the black-and brown-banded species is considered the true banded woolly bear.

Woolly bears share winter predictions with some of nature's other critters, like honeybees and yellow jackets. Folklore tells that honeybees will store honey en masse in preparation for a severe winter and yellow jackets will build nests either high in the trees or in the ground depending on what the coming winter has in store.

Bloetscher, who eyes her honey bees' behavior and jokingly predicts winters for her friends and colleagues, believes that such folklore gives stability to something people have no control over.

"I think people have this basic need to be prepared, to be forewarned of what the weather has in store for them," said Bloetscher. "That's probably why they make a connection with animal behavior or appearance. It gives them some sort of control over the future."

Not to miss out on all the woolly bear fun, a tongue and cheek survey conducted by this writer over a three-day period in the metro Columbus area uncovered four woolly bears. All had long brown bands, suggesting a mild winter. According to the Old Farmer's Almanac, temperatures through January in the Greater Ohio Valley will be milder than normal with below normal snowfall. Could the woolly bears be right? Only time will tell.

Candace Pollock
Barbara Bloetscher