Woolly Bear: Nature’s Weather Predictor

A Wooly Bear Caterpillar walks on branch early in the morning after rain.

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.

It is doubtful that the color of the woolly bear’s coat reliably predicts the length of the winter, or that the depth of snow somehow correlates with the thickness of woolly bear fuzz, but their fall migration remains a reliable sign of impending weather.

Becoming the Banded Tiger Moth

The larvae of most tiger moths are usually hairy — and are frequently called woolly bears. Here’s a little more about the tiger moth:

  • Tiger moths are often attracted to lights at night.
  • This moth mostly occurs in and around fields and lawns, parks, disturbed areas, in both rural and urban settings.
  • Adults fly from March or early April into October.
  • There are likely¬†two broods of tiger moths in Missouri.
  • Most tiger moths overwinter as full-grown caterpillars or in the pupal stage.
  • Their cocoons usually contain caterpillar hairs.

Discover more about¬†the banded tiger moth with the MDC’s Field Guide.

Is it a moth, or is it a butterfly? Learn the differences between the two in the video below.