Behind the Weather Folklore: Woolly Bear Caterpillars

Before there were meteorologists predicting the upcoming Old Man Winter season, there was weather lore!


What You Need To Know

  • Folklore says the upcoming winter can be predicted by the stripes on a caterpillar
  • They say the wider the black band is, the worse the winter will be
  • Milder winters are predicted by a wider brown band on the caterpillar
  • While fun, these ideas are not factually true and are based on other factors

A famous weather saying:  Does the stripe on the back of a woolly caterpillar indicate the severity of the upcoming winter?

This saying is popular across New England and the Midwest, especially as winter draws nearer each year. 

Known for their fuzzy nature and black bands, they’re sometimes called woolly bear or fuzzy bear caterpillars. They are often found in the fall season, right before winter!

The caterpillar will leave their plants, usually a variety of grasses and weeds, in search for a spot to hibernate for the winter.

There are two sides to every story, and in this case there are two versions of this famous weather saying!

Folklore Breakdown

In the fall, the amount of black on the woolly caterpillar is linked to the severity of the upcoming winter. It’s important to note that the black varies not only in each season but in different areas too.

According to the legend, the longer the woolly bear’s black bands, the longer, colder, snowier, and more severe the winter will be. Also the wider the middle brown band is the milder the upcoming winter will be. 

And if you look closer, supposedly the position of the longest dark bands indicates which part of winter will be coldest and hardest. So if the head end is dark then the beginning of winter will be worse. If the opposite end is dark, the end of winter will be colder.

Plus the 13 weeks of winter, according to the folklore, correspond to the 13 segments to the caterpillar’s body!

Apparently the caterpillar’s coat will indicate the upcoming winter season severity. The ‘woolier’ the coat, the colder the winter. 

Another version deals with the woolly caterpillar’s direction of travel. Basically it states that if it’s crawling in a southerly direction then they’re trying to escape winter’s cold from the north. And if the woolly bear is moving north, then it’s a mild winter.

Folklore Popularity

The myth has been around as far back as colonial times. However, it began to grow after Dr. Howard Curran’s study in 1948 was published.  He counted the brown bands on 15 different specimens and made a winter prediction. 

However the legend’s popularity spread in modern times because of several festivals honoring them!  Just like the famous groundhog, Punxsutawney Phil, people celebrate the woolly bear’s winter prediction and the weather folklore.

In fact, there is an annual festival in Vermilion Ohio, “Woolly Bear Festival”. The festival started in 1973 and in part created because of Cleveland’s longtime weatherman, Dick Goddard. 

Another famous festival in Banner Elk, North Carolina called “Woolly Worm Festival” where there are worm races held! And there are festivals all over the country honoring the famous woolly bear legend.

Fact or Fiction?

Fiction. As much fun as it is to search for the woolly worm each fall, don’t get your hopes up, the caterpillar can’t predict what Old Man Winter has in store for the upcoming winter season. 

According to the National Weather Service, the caterpillar’s coloring is based off it’s age, how long it’s been feeding, and different species. In North America, there are over 200 species.

The better the growing season the bigger the woolly worm will grow. Also the width of the banding is an indicator of the current or past season’s growth.

So basically the coloring and size of the woolly worm indicate the growing season that year or the year’s past instead of the winter season.

Caterpillars shed their skins several times before reaching adult size, and their colors change with their age too. As a result, there are so many different colors and hair variations that we may see each fall that can vary the folklore’s results.

The woolly caterpillar’s coat helps them survive Old Man Winter each and every year. The worm can survive temperatures as low as –90 degrees! They can live up in the Arctic where they can spend an entire winter frozen in an ice cube! 

Lastly, the caterpillar travels north/south, and east/west…the worm is in search of a place to curl up and hibernate for the winter. And that is all, they just want to sleep for the winter in a good, dark, sheltered spot.

By springtime the caterpillar forms a cocoon, and a few weeks later become an Isabella tiger moth which is active at night throughout the summer.