Does pyrrharctia Isabella predict a harsh winter?

The scientific name might not ring a bell, but the common woolly caterpillar—or woolly bear or fuzzy caterpillar—is one of the most commonly seen caterpillars and is famous as a predictor of winter weather. In the fall the woolly bear begins its quest for a dark, hidden place—under rocks, logs or other protected spots to overwinter.

Let us know your woolly prediction for this year’s winter season. Email

Whether out walking or driving, the caterpillar on the move is easy to spot, with black bands on its front and end with reddish brown bands in the center. According to lore, the larger the brown band, the less severe winter will be. The more black on the caterpillar, the more harsh will be the upcoming winter weather.

Some believe the nature of the caterpillar’s travel is also an indicator of winter weather conditions. A woolly bear traveling south is hoping to overwinter in warmer climes to escape bad weather, while a caterpillar headed north is confident the season will be mild.

The 13 bands of the caterpillar, be they black (bad weather) or brown (warmer weather) can be indicators of when the worst or mildest weather will fall. A woolly bear with more black at its head indicates the severe weather will hit early, and more black at the back indicates the last weeks of winter will be severe. Some folklore credit each of the 13 bands with prediction of each of the 13 weeks of winter for pinpoint prediction.

According to the Farmer’s Almanac, a curious curator of insects for the American Museum of Natural History in New York City put the woolly to the test in a series of experiments. From 1948 to 1956, C.H. Curran captured woolly bears to examine their color patterns and made weather predictions, which were published thanks to a reporter friend of his. He claimed the woolly was quite accurate.

Science says otherwise. The woolly bear hatches from an egg in the spring and eats during the summer. As it grows, the bear molts—as many as six times in a good feeding cycle. At each molt, there is less brownish coloration and more black. It would seem the amount of each color on the woolly bear depends on how good a season it has just experienced rather than what is to come.

Woolly bears are the larva of the Isabella Tiger Moth and belong to the bristled species of caterpillar. The bear is joined as an indicator of winter weather with bees and wasps, according to folk lore. Bees are said to hoard extra honey if winter will be harsh, and wasps are said to determine their overwinter nests according to the coming weather. Similarly, a heavy acorn production is said to mean a harsh winter is coming.

We would like readers to let us know what prediction for winter they are seeing in their own woolly bear bands. Please e-mail any comments or photos to, or mail or drop off at our office at 331 Northland Drive, Rockford, MI 49341.

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