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An Unusual Weatherman in the Woolly Bear

Have you ever picked up an orange and black woolly bear to figure out the winter forecast? Anyone who grew up in the North (they seem to be more common up there) might remember hearing about how the stripes on a woolly bear would tell you how severe the winter would be. These caterpillars aren’t quite that clever but they do have a fun history, according to some information from The Old Farmer’s Almanac.

  • The woolly bear caterpillar is the larval form of the Isabella tiger moth. It’s common from Northern Mexico through the United States and across the southern third of Canada.
  • They are more bristled than woolly with short, still bristles of hair.
  • Like other caterpillars, they hatch during warm weather from eggs laid by a female moth.
  • Mature woolly bears search for wintering sites under bark or inside cavities of rocks or logs. You’ll often see them crossing the road or sidewalk during the fall as they look for a place to spend cooler weather.
  • When spring arrives, woolly bears spin fuzzy cocoons where they transform into full-grown moths.
  • Woolly bears are the most recognizable caterpillar with black bands at each end and a middle band of orange or brown.

So how did the woolly bear get a reputation as a weatherman? The Old Farmer’s Almanac explains the legend in this way: supposedly the wider the middle brown section of the woolly bear, the milder the coming winter will be. So a narrow brown or orange band means a harsh winter.

Dr. C.H. Curran, curator of insects at the American Museum of Natural History in New York City in the 1940s, did some weather-related research on the woolly bear. Between 1948 and 1956, he found the brown segments of the woolly bear took up more than a third of their bodies. Those wide brown segments corresponded with milder than average winters.

Dr. Curran didn’t place real scientific proof in his experiments but they did help give more credibility to the legend of the woolly bear and resulted in fun speculation. In fact Banner Elk, N.C., hosts the Woolly Worm Festival each October complete with a caterpillar race. 

Have you seen any woolly worms this year? Tell us your prediction for the winter!

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