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Woolly Bear Caterpillars: Identification and Winter Weather Lore

a woolly bear or a woolly worm caterpillar, brown and black, on pavement.

Based on the measurements of the distinctive woolly bear caterpillar, you can figure out your weather forecast!

Image Credit:
University of Missouri
Written By: Jess Sullivan Digital Editor

Woolly bear caterpillars—also called woolly worms—have long been said to predict winter weather. According to folklore, the wider the rusty brown band on the woolly bear’s body, the milder the winter. More black? A harsher season may be ahead. 

Before making your own winter forecast, take a closer look! Not every fuzzy caterpillar is a woolly bear, and even woolly bears can vary in color. Here’s how to identify one and read its bands.

How to Identify a Woolly Bear Caterpillar

If you see a black and brown fuzzy caterpillar, there’s a good chance it’s a woolly bear! The banded woolly bear is usually black on both ends and rusty brown in the middle, though some are mostly—or even entirely—black or rusty brown.

White or yellow fuzzy caterpillars are often different species, some also called “woolly bears,” rather than the familiar banded woolly bear of winter folklore.

The woolly bear caterpillar is the larva of the Isabella tiger moth (Pyrrharctia isabella), which has yellow-orange and cream wings spotted with black. Alas, the moths are not known for their weather-predicting abilities.

Banded woolly bear caterpillar with black ends and a rusty-brown middle beside an Isabella tiger moth
The woolly bear caterpillar (left) grows into an Isabella tiger moth (right).
Credit: SillyPuttyEnemies / Andy Reago & Chrissy McClarren

What Do Woolly Bear Colors Mean for Winter?

The woolly bear caterpillar has long been associated with winter weather. According to folklore, the woolly bear’s 13 body segments represent the 13 weeks of winter. Here’s how to read its colors:

The wider the rusty brown sections (or the more brown segments there are), the milder the coming winter will be. The more black there is, the more severe the winter. 

Love weather lore? Read about more signs of a hard winter. 

winter weather folklore, using a woolly bear caterpillar to predict winter

Can Woolly Bears Really Predict Winter Weather?

That’s part of the fun of woolly bear folklore! Their colors aren’t a proven way to forecast winter, but one entomologist decided to put the legend to the test.

Between 1948 and 1956, Dr. C. H. Curran counted the rusty-brown segments on woolly bears. His counts suggested milder winters—and lo and behold, the winters that followed were milder than average! Still, Curran knew his samples were small. He was having fun with an old tradition, not claiming a scientific breakthrough.

Try Your Own Woolly Bear Winter Forecast!

Spotted a woolly bear? Take a look at its black and rusty-brown bands and make your own winter prediction! Do your fuzzy forecaster’s predictions match the Almanac’s winter outlook?

Watch a woolly bear in action in this short video!

Whether it’s fact or folklore, we always enjoy the fun! Share what your local woolly bears are predicting in the comments below.

Frequently Asked Questions

  • Is a woolly bear the same as a woolly worm?

    Yes! “Woolly bear” and “woolly worm” are both common names for the black and brown banded fuzzy caterpillar that becomes the Isabella tiger moth. You may also see them written as “wooly bear” or “wooly worm,” with one “l.” Despite the nickname, it’s a caterpillar, not a worm.

  • What do woolly bear caterpillars eat?
    Woolly bear caterpillars eat the leaves of low-growing plants—think dandelions, plantain, dock, asters, goldenrod, and even some grasses.
  • Are woolly bear caterpillars poisonous or safe to touch?
    No, woolly bear caterpillars aren’t poisonous or venomous. They don’t sting, but their bristly hairs can irritate sensitive skin. The safest bet is to enjoy watching them without picking them up.
  • Where do woolly bear caterpillars live?
    Woolly bear caterpillars live all over North America—from the United States and Canada down to Mexico. Look for them around grasses and weeds. When fall rolls around, you might spot them seeking shelter under bark, rocks, logs, or a cozy pile of leaves to ride out the winter.
  • What do woolly bear caterpillars turn into?
    Woolly bear caterpillars become Isabella tiger moths (Pyrrharctia isabella), with cream and yellow-orange wings spotted with black. After spending winter as caterpillars, they spin cocoons in spring and emerge as moths.
Weather Lore
Sources
  1. National Weather Service — Woolly Bear Caterpillar - Winter Predictor Or Not?
  2. Iowa Department of Natural Resources — Winter Is Coming: Can the Woolly Bear Predict It?

About The Author

Jess Sullivan

Jess Sullivan

Digital Editor

As Digital Editor of The Old Farmer’s Almanac, Jess is dedicated to bringing readers content that is accurate, clear, useful, and engaging. She has years of experience crafting written communications ...

Read more from Jess Sullivan

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Comments

<span>Lisarenee</span> Wed, 02/08/2012 - 08:32
Not sure if it is the "Woolly Bear" I've always used to predict the winters in NE Indiana or something different (because I've seen such a wide variety over the years)-- but I always called them "Woolly Worms" . . . My parents always told me simply that the lighter the color the harsher the winter and I'm pretty sure it has always been correct. I remember seeing white ones and then having a very harsh winter. As an adult I don't always see them but this past fall I saw more of a yellow color one . . . so far it has been a realatively mild winter. My prediction was, "It will not be a harsh winter--more of an 'inbetween' winter." Again, I don't know if what I look at is the "Woolly Bear."
<span>Secarpenter</span> Wed, 01/18/2012 - 17:44
I found a Woolley bear under some of my wood that's piled up all curled up in 27 degree weather on January 18th 2012. I thought it was dead because how cold it is outside but when I brought it inside it eventually opened up and started crawling around everywhere. It's really strange to find an alive one in the middle of the winter. This one has a wide black stripe where it's head is and long brown/orange middle and a short black tip. I live in Radnor Ohio and so far this winter it has been very wet and mild. Maybe 2 inches of snow all winter here so far.
<span>Becky12345</span> Tue, 11/15/2011 - 10:33
We had an ALL BLACK Woolly Worm in our driveway over the weekend, in Garner NC. It could mean a COLD Winter!! I put him in safe area under some bushes.
<span>Kevin Hull</span> Thu, 11/03/2011 - 03:00
I Found an all black "Woolly Bear Caterpillar" on North Colonial Dr. Cortland, Ohio. I also have three friends in the same area, with one in Champion, Ohio that found all black ones too. As my father, God rest his soul....used to say. It's gonna be a very bad winter. Nov.2,2011.
<span>Gradofan</span> Fri, 10/14/2011 - 21:46
RE: the number of wooly worms this year - it all depends on where you are. There are almost none in Illinois this year - very odd, indeed! Maybe they've gone the way of the honey bees.
<span>Falltime</span> Sun, 10/09/2011 - 19:03
Does the fact that we seem to have sooo many woolly bears have anything to do with predicting the weather? I don't remember a time when there has been so many. Dodging them in the road is a challenge!
<span>Halleycomet</span> Sat, 10/08/2011 - 15:55
Here in waaaaayyyy Upstate New York on Vermont border we are just now seeing Wooley Bears for the first time this year. Alll so far have been even between black front, orange middle, and black rear. The "lore" I have always heard is that the segments predict how long each portion of the winter will be---front section is for Fall and Early winter; middle for mid winter and rear for end of winter shading in to spring. This does correspond with a harsh or mild winter if you think about it just not direct temperatures. Altho we have very few squirrels out here in Farm Country (go figure!) we have a bumper crop of black walnuts on yard trees and have seen LOTS of acorns on trees and ground. Have seen LOTS of foxes recently many more and with more fur than you would expect. More road kills than usual among all furry things---does this mean they are more active looking for food? And baby skunk in the daytime last week! Enjoying introducing very curious grand daughter to Wooley Bears and lady bugs etc but NOT so much the incredibly ANNOYING and prolific "Biting flies" that followed the recent flooding here. What is UP with THAT??????
<span>Kimbo96</span> Thu, 10/06/2011 - 11:26
I just saw a woolly bear ALL ORANGE with just alittle black band around face. What does that mean? I live in upstate NY
<span>Kimmp</span> Tue, 11/08/2011 - 20:45
I'm upstate as well, in the Finger Lakes area right near Lake Ontario. I have fou d 3 woolys that had a little black on head and tail and a big band of brown/orange. A friend of mine is finding the same. I haven't seen this much brown/orange on one in quite awhile. Livestock don't look too shaggy coated either. I can only hope it will be mild, as I absolutely hate winter.
<a title="View user profile." href="/author/editors">The Editors</a> Fri, 10/07/2011 - 11:16

Hello, it might have been a different variety. According ro folkore, the narrower the brown (orangish) band on the woolly bear caterpillar, the more severe the coming winter.