While all bears are preparing for the winter, it's the familiar fuzzy caterpillar known as the woolly bear that clearly signals that cold weather is just around the corner.
On sunny autumn days, woolly bear caterpillars cross roads and highways. But even before there were paved roads, people noticed the woolly bear migration. Woolly bears were the weather predictors of folklore.
As the days grow shorter and the nights grow cooler, most green plants stop growing. Woolly bears are leaf-eaters, and they are quick to notice the shortage of food. Since caterpillars can't migrate south, their only option is to find a protected place to spend the winter.
Hollow logs, piles of leaves, cracks in foundations and stacks of firewood are all good places to hide. Woolly bears cross roads in droves as they look for winter dens.
The thickness of their bristles were seen in folklore as a snow predictor. However, they function less for warmth on woolly bear caterpillars and more for helping them to freeze over more controllably. The brown to black ratio is more an indicator of their age and how long they've been feeding than mild or harsh winter predictions. You can learn more in the video below.
The fall migration of woolly bear caterpillars still remains a reliable sign of impending weather.
To discover more about the woolly bear, visit MDC’s Field Guide.