Fast Fact: Woolly Bear Caterpillars

Have you ever seen one of these brown and black caterpillars? These are woolly bear caterpillars, and they grow up to be Isabella tiger moths, an orangish or yellowish-brown moth. According to an old legend, these fuzzy caterpillars can predict how bad of a winter we will have. As the legend goes, the wider the caterpillar’s middle brown band, the worse the coming winter will be. There’s no truth to this, though. Instead, the color and width of the bands has to do with their diet and age.

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While these caterpillars can’t be used as a reliable winter weather forecast, they do have an unusual way of surviving winter. They withstand freezing temperatures much like your car does. They produce a substance called glycerol, which is like antifreeze. When temperatures drop, the caterpillars freeze, but the glycerol prevents their inner cells from freezing. This allows them to survive even the coldest of winter weather.