The Woolly Bear Caterpillar

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Bill Steffen Weather 101721

I came across this critter on the walking path at the Alpine Athletic Center on Sunday. This is a woolly bear caterpillar. It has black-colored ends and a band of brown color in the middle. It turns into the Isabella Moth:

Legend has it that you can look at a woolly-bear (sometimes called woolly-worm caterpillar) and predict the severity of the winter by looking at the 13 bands or segments of the caterpillar. The ends of the woolly bear are black and the middle is brown. The fatter and more prominent the brown segments – the milder the winter will be. The blacker the caterpillar is, the colder and snowier the coming winter will be.

A man named C.H. Curran, who was curator of insects for the American Museum of Natural History did his own small study on the woolly-bears from 1948-56 and concluded they did have some predictive value, though he cautioned that his sample was far too small to draw any conclusions.

Native Americans watched Canada geese fly south in the fall. The geese started their journey south when it got cold in Canada. If it got cold early, they flew south early. The geese were reacting to current weather in Canada. The Native Americans knew that an early flight south was often followed by a hard winter. So, the geese had predictive value to those smart enough to recognize it.

The woolly-bear is pretty much all black when it emerges from the egg. As it matures, it develops more of the reddish brown. Since it’s cold-blooded, the rate of development would be a little temperature dependent. We have had warmer than average weather in West Michigan since July.

You can find them over a good portion of the U.S. and Southern Canada. There are woolly-bear festivals in Ohio, New York, Pennsylvania, Kentucky, North Carolina and Ontario.

See if you can find a woolly-bear and check to see how much of it is brown. Then in the spring, you can know if your little caterpillar made a good forecast.

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