Native American Cold Weather Forcast

Can the Woolly Caterpillar Predict the Severity of the Winter?

Oct 18, 2009

A popular American legend, inherited from Native Americans, is that the woolly bear caterpillar can predict the severity of the coming winter. Is it a myth or fact?

The woolly bear caterpillar is well recognized throughout North America. According to the United States Geological Survey, "Caterpillars of Eastern Forests," they are often seen because they eat during the daytime, along roads or low vegetation. Autumn stimulates them to grow a black bristle coat, which looks like fur. As the caterpillar grows, the coat forms rust colored bands. When mature, all of the fur is rusty orange.The caterpillar hibernates through winter, spins a silky cocoon in spring and emerges into the orange Isabella Tiger moth.

The Legend

Today many think the mere appearance of the woolly caterpillar is a prediction of a harsh winter. Or we forget if the orange rings mean a long or short winter. The legend dates back to the Native American Indians who taught colonists about the woolly bear caterpillar's ability to presage the winter weather. In the the article, “Woolly Bear Caterpillars: Weather Predictors?” in the 1999 Old Farmer's Almanac, the real tradition is that more and wider rusty orange segments on the woolly bear caterpillar predict a winter that will be less severe than usual. If the orange rings are thin or few, the winter will be harsh.

In 1948, a biologist named Charles Curran set out to Bear Mountain State Park. For eight years he collected woolly caterpillars and studied the length of orange bands. He then predicted the severity of the coming winter (Rozell,1996). Some regard this as the authoritative study of the myth.

The Woolly Bear Becomes Famous

The Almanac article claims that Curran, his wife and some friends had formed a group, the “Original Society of the Friends of the Woolly Bear,” and went to Bear Mountain in the fall simply to enjoy the foliage. Curran’s predictions, however, became widely known, much anticipated and made the woolly caterpillar legend famous. Thirty years later, Bear Mountain Park revived the tradition and makes a long range winter weather forecast based on the caterpillars' rings.

The Truth about the Woolly Bear Myth

Whether for pleasure or science, Curran’s predictions were accurate for the first three years and then went awry. He also found that different populations of caterpillars living close by had entirely different color patterns (Rozell, 1996). The United States Geological Survey (cited above) has determined that the rusty rings indicate how near the caterpillar is to full growth before autumn weather stimulates it to seek a winter shelter, and is not related to winter weather at all.

Paraphrasing a quote in the Almanac article, Mike Peters, an entomologist at the University of Massachusetts, said there might be a relationship between the weather and the woolly bear stripes. The number of brown bands might show how late in the spring the larva hatched from its egg. But that would only tell us about the severity of the last winter!

A Native American Tradition Adopted and Revived

Although the woolly bear caterpillar may not be a weather predictor, its fame as a harbinger of winter is entrenched in our culture. The woolly is furry and cute. The woolly bear is probably the only caterpillar that most people like to pick up and watch as it curls into a little ball. It is still beloved by many, and its place of honor in forecasting the winter weather will endure as a cherished American tradition.

Reference:

Rozell, NA, “Balmy or Biting Winter Ahead? Ask the Bears,” Alaska Science Forum, Article #1303.September 18, 1996.

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