The woolly bears are out, can they really predict the upcoming winter?

The first fall sighting in the southwest suburbs of the fuzzy and fast-moving caterpillar

woolly bear caterpillar, the larva of the isabella tiger moth(photo by author)

I know it's fall in northern Illinois when the trees are filled with colorful leaves, the air is crisp, Halloween decorations are everywhere to be seen, and I have a pumpkin spice latte in my hand. And one other thing, fuzzy black and rusty red-banded caterpillars are racing across my path when I'm out for a walk in the morning.

I spotted my first woolly bear today, and it was moving quickly from one side of the walking path to the other. It must have been after the grass on the other side because once it reached it, it slowed down and might have been munching, although it was hard to tell.

As I watched it, I looked for the size of the black bands, which are supposed to predict the upcoming winter. The folklore says the more black on the caterpillar, the more snowy, cold, and frigid of a winter we can expect.

This woolly bear seemed to have a pretty thick reddish-brown band. So does that mean Chicago can expect an easy winter?

As I thought about it, I wondered, how would a caterpillar possibly be able to predict the weather? And what would the coloring of its bands have to do with it? What's the story behind this? Could there be any truth behind the old wive's tale?

What are woolly bears?

They are the larval stage of the adult isabella tiger moth. They can be seen in the fall in Illinois crossing roads and paths. They are about two inches long with stiff bristles of black and reddish-brown bands.

Adult isabella tiger moth(JGanance/CC BY-SA 4.0/Wikimedia Commons)

And somehow, they are known for predicting the weather. The superstition is, the longer the black segments are on the caterpillar in relation to the rusty brown bands, the more severe winter will be.

Is there any truth to the myth?

Fortunately for my curiosity, according to the University of Illinois Urbana-Champaign extension, some entomologists also wondered if there was anything behind the folklore.

The scientists measured the width of the orangish band on the caterpillar and compared it to the following winter. Sadly, they found there was no correlation between the size of the bands and the severity of the next winter.

The short answer is, no, woolly bears cannot tell us what kind of winter is coming.

woolly bear caterpillar found in the southwest Chicago suburbs(Photo by author)

But there is something to the story

The entomologists did find the colors of the fuzzy caterpillars might relate to the previous winter and the length of summer. In the spring, the woolly bears start with all-black hair. Their reddish-brown bristles grow during the warm weather.

The longer the summer, the more brown hairs, and the less black. Shorter summers and colder falls meant more black and less brown.

So, no, it's not a prediction of future weather, but it's an interesting piece of trivia you can tell someone the next time they try to tell you what kind of winter we have coming based on a fast-moving fuzzy caterpillar in your path.

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