Woolly bear caterpillars are the stuff of folklore – they are much sought after in some parts of the states. But what do the colors of a woolly bear mean? What is this legend, and how true is it? Let’s learn all about it!
The woolly bear, also known as woolly worm and fuzzy caterpillar, is the bristly caterpillar of the Isabella Tiger Moth.
They start to appear somewhere around early fall. There are two generations of woolly bears each year, the second generation that comes out around fall being more noticeable.
The colors of these fuzzy-looking creatures are said to be predictors of the upcoming winter. Woolly bears have black bands on both ends of their body and a reddish-brown color in the middle.
The legend goes that the longer the black bands, the more severe and long winter will be. Similarly, the wider brown band represents a mild winter.
In this article, we explain this legend, its origins, the truth behind it, what science says, and a lot more.
What Is a Wooly Bear Worm?
The woolly bear caterpillar is a common worm found across the US, Canada, and Mexico. There are typically two generations of woolly worms in a year, once in spring and once in summer.
After hatching from the egg, the larva feeds for a few days before pupating and hatching as a tiger moth. The lifespan of the moth is relatively short, as it dies shortly after mating and laying eggs.
In colder temperatures, the larva freezes solid throughout winter before breaking out and pupating.
In warmer climates, however, the caterpillar will feed for a couple of weeks after hatching before pupating.
These woolly creatures’ life cycle highly depends on their surrounding environment and temperature.
Interestingly, these fuzzy caterpillars curl into a tight ball and play dead when picked up or disturbed.
The Wooly Bear Folklore
The woolly bear caterpillars and their body colors are associated with several folklore and legends that say they can predict the weather.
These orange and black creatures start becoming visible during fall after they leave their food plants in search of darker spots to hibernate.
Thus, appearing right before winter, the color, size, and position of their fur coats have become synonymous with a winter forecast.
The most well-known folklore of the woolly bear correlates the color of its fur with the severity of the upcoming winter.
The woolly bear has black colored bands on both ends of its body, while the middle part is brownish red or orangish.
The legend goes that longer black bands on the woolly bear’s body depict a whiter and chiller winter coming up,
The wider the brown section is on its body, the milder the forthcoming winter will be.
Some forecasters also say that the woolly caterpillar’s body, segmented into 13 sections, represents 13 weeks of winter.
The orange bands signify milder winter weeks, while the black bands indicate the weeks of severe winter.
The black bands’ position is also apparently an indicator of the season.
A dark band near the head signifies that the winter will start with a bang, getting as chill as possible. And if the tail band is darker, the end of winter will be severe.
In another version, the woolly bear’s fur coat also represents what kind of winter it will be. If its coat is thicker and woollier, it will be a colder winter.
One final version talks about the woolly worm’s direction of travel. If it is seen traveling north, it will be a milder winter.
However, if the woolly bear is on a southward path, it indicates a colder winter.
C. H. Curran And His Experiment
The tale associated with the woolly worm persuaded entomologist Dr. C.H Curran to conduct an experiment in 1948.
At the Bear Mountain State Park near New York City, Dr. Curran collected as many woolly worms as he could in a day.
By observing the reddish-brown segments, he made a prediction for the upcoming winter through a reporter friend.
Over the next eight years, Dr. Curran continued his experiment to establish a scientific correlation.
During those years, his sample caterpillars had brown bands that were ⅓ the size of their body. And the winters during those years were, in fact, fairly mild.
However, this wasn’t enough evidence to establish any real scientific connection. His sample sizes were too small to produce any significant data. But folklore became even more popular than before.
Can A Wooly Bear’s Bands Really Predict Weather? Reality vs. Myth
Despite the popular legends and woolly worm festivals, scientists and entomologists say that these fuzzy worms cannot predict the winter.
There are scientific and evolutionary reasons for the colors and fur of these fuzzy worms. Woolly bears’ coloring depends on their age, species, and how long they’ve been feeding.
If the growing season has been good, they grow bigger. This results in narrower brown bands on their bodies.
Secondly, the caterpillar sheds its skin six times before maturing into an adult. With every successive shed, the colors change, becoming more reddish and less black.
Thirdly, there are around 260 species of tiger moths, each with distinct color patterning and variations.
So you could be seeing any of these species with any number of color combinations. It has nothing to do with how the upcoming winter will turn out.
As far as other legends go, the thickness of their fur or setae does not predict the severity of winter. It’s also not present to protect the caterpillar.
Instead, it helps them freeze controllably to hibernate during winter. Similarly, their travel direction is entirely determined by their search for a spot to curl up and hibernate.
Frequently Asked Questions
What does it mean if a woolly bear is all black?
If you see an all-black woolly bear, it does not mean that there will be a severe upcoming winter. You are likely seeing an altogether different species.
The Giant Leopard Moth Caterpillar is black and has bristles like the woolly bear. It has nothing to do with winter prediction.
What does it mean when a woolly bear caterpillar is all orange?
If you see an all-orange caterpillar that looks like a woolly bear, you’re likely seeing a Yellow Bear Caterpillar.
Or it could be a different species of the tiger moth. This is not indicative of a milder upcoming winter. These caterpillars look like this all the time.
What does it mean when a wooly worm is more brown than black?
There are scientific reasons why the woolly worm is more brown than black. Woolly worms shed their skins six times before turning into an adult.
With every successive shed, their fur becomes browner in color. So it’s possible that the worm you see is at a further stage to mature into an adult.
What does a white wooly bear mean?
Woolly worms are black and orange. If the worm you see is white with bristles like the woolly bear, it’s most likely the Hickory Tussock Moth’s larva.
Or it could be a species of the Virginia Tiger Moth. Either way, the color is not a prediction of the upcoming season.
The woolly bear caterpillar, with its fall color palette of black and orange, is the caterpillar of the Isabella Tiger Moth.
It is seen right before winter and is famously associated with weather prediction legends.
However, entomologists state there are scientific reasons behind this fuzzy worm’s color and fur that, for years, have become the stuff of legends.
Thank you for reading.
The legends and stories about woolly bears have also inspired our readers to ask us about the symbolism and legends that surround these creatures.
Learn all about the fun, folklore and stories that they have shared with us over the years in the emails below.
Letter 1 – Isabella Tiger Moth Life Cycle
Isabella Tiger Moth eggs, etc Hello Bugman. I just found your egg page and I absolutely love it! I thought you might like these photos of Isabella Tiger Moth laying eggs and the resulting larve, otherwise known as Wooly Bear Caterpillar. She laid the eggs on my door jam, and I am rearing them, at least until fall. They overwinter as caterpillars so I won’t try to keep them all winter. They are eating nettles. Betsy Hi Betsy, We hope you will continue to provide us with Isabella Tiger Moth, Pyrrharctia isabella, metamorphosis images as the caterpillars grow and pupate.
Letter 2 – Mating Southern Cyan Tiger Moths from Costa Rica
Interesting Costa Rican Wasp Moths – Part 3 Interesting Costa Rican Wasp Moths – Part 3 To round out my little set of Costa Rican Wasp Moths, here is a pair of Southern Cyan Tiger Moths (Macrocneme chrysitis). This is another day flying Ctenuchid (Arctiidae: Ctenuchinae) and an obvious wasp mimic. The species ranges throughout the tropical Americas, as for north as south Texas. These were also photographed at the Las Cruces Biological Station/Wilson Botanical Gardens. Regards. Karl Hi again Karl, We wrote back the day you sent this and indicated we would post it upon returning home from work, but political activism got in the way, and it wasn’t until this morning that we were reminded that we had neglected your wonderful submission. Since the quantity of mail we are receiving has drastically increased with the arrival of spring, we had to dig back several pages to locate you awesome image. Sorry for the delay. According to the North American Butterfly Association (NABA) website, the species may also be found in Texas.
Letter 3 – Mating Painted Tiger Moths
mating gray/white/black moths Location: hill above San Mateo, California October 10, 2010 7:31 pm I found these two moths, happily oblivious to me, on steps in a yard on the San Francisco peninsula of California. Its a hilly area of grass, shrubs and oak trees. I’d love to get a Latin name for them. Some more photos here: http://www.facebook.com/album.php?aid=24023&id=100000839873534&l=551cb22641 Signature: Craig Reynolds Hi Craig, These little beauties are Painted Tiger Moths, Arachnis picta, and they are a common species in Southern California. The caterpillars are of the Woolly Bear type.
Letter 4 – Now in Southern California: Mating Painted Tiger Moths
Ed. Note: October 13, 2016 We are also finding Painted Tiger Moths at our porch light in Mount Washington, Los Angeles, so it is fair to say they are currently flying in Southern California. Subject: Strange creature Location: Soquel Ca October 11, 2016 7:07 pm What the heck is it??? 2 heads!!! Signature: Eve Dear Eve, The reason there are two heads is that one head belongs to the larger female on the right and the other to the male. This is a mating pair of Painted Tiger Moths, a relatively common California species that is most common in winter months. wow you are awesome to get back to me thank you! , I just figured it out!!!! how embarrassing!!!!! as one has left and eggs are in the place, so funny I really thought it was a 2 headed thing and not a couple!!!! jeez are they good for the garden? Thanks again The larva of the Painted Tiger Moth is a Woolly Bear that is a general feeder that is quite fond of weeds, so one could argue that though the adults do not eat and do not pollinate plants, the caterpillars can help keep back weeds. The diet of the caterpillars is described on BugGuide as: “Larvae are generalists of low herbacious plants.”
Letter 5 – Mating, sexually dimorphic Window Winged Moths from Thailand
Subject: Unidentifiable Bug Location: Northern Thailand August 2, 2017 10:22 am Hello, I have been trying to figure out what the heck these bugs are. They appear to be mating, have antenna, wings and small but articulated bodies. We came across them in early May in Northern Thailand. I’m hoping you may be able to help! Cheers, Signature: Duke Dear Duke, This is definitely a mating pair of moths, and we are relatively certain they are Tiger Moths in the subfamily Arctiinae. They exhibit extreme sexual dimorphism meaning the two sexes do not look alike. We cannot find anything similar on Farangs Gone Wild. We will contact Tiger Moth expert Julian Donahue to see if he recognizes them. We would not rule out that they might be in the Clearwing family Sesiidae. Correction Courtesy of Karl Hello Daniel and Duke: These are a Picture-winged Leaf Moths (also known as Window-winged Moths), in the family Thyrididae. The species is probably Glanycus insolitus, although there are a few similar species. The iNaturalist site has a similar photo of a mating pair. Regards, Karl Julian Donahue’s Response September 4, 2017 Hi Daniel, This arrived while we were on a month-long birding trip to Indonesia, but I see that someone has already identified them as thyridids (many of which are very leaf-like, but these are spectacular). Julian
Letter 6 – Mating Tiger Moths from Thailand
Subject: Identity of Two Winged Bugs Geographic location of the bug: Thailand Date: 09/15/2017 Time: 01:36 AM EDT Salutations! Can you possibly identify these fabulous bugs? I can’t find anything on them. Some are exquisite, some terrifying, but all are utterly rivetting! Thank you very much. I’m sending a few others, too. How you want your letter signed: Suzanne Jamsrisai Dear Suzanne, These mating Tiger Moths are excellent wasp mimics. We found a FlickR posting that looks like your species and it is identified as Amata sperbius. INaturalist has numerous Asian sightings.
Letter 7 – Newly Eclosed Tiger Moth
Subject: Black and yellow bug, 1cm long Geographic location of the bug: Huntsville, Alabama Date: 07/29/2018 Time: 12:18 AM EDT Your letter to the bugman: This bug is on curtains in my closet, here in north Alabama. It is about 1 cm long. What do you think it is? I have enjoyed your page for many years. Thank you for what you do! How you want your letter signed: Elizabeth Simmons Dear Elizabeth, This is a newly eclosed Tiger Moth in the subfamily Arctiinae. Since it has recently emerged from the pupal state, its wings have not yet fully expanded and hardened. Based on BugGuide images, we believe it is in the genus Apantesis, formerly Grammia. It poses no threat to you or your home.
Letter 8 – Newly Eclosed Tiger Moth
Subject: Very Cool Moth Geographic location of the bug: Central Virginia Date: 05/20/2019 Time: 10:35 AM EDT Your letter to the bugman: I came across this moth while mowing. Made sure to move it before going through. Thoughts? How you want your letter signed: Mr. Motter Dear Mr. Motter, This Tiger Moth appears to be newly eclosed and its wings haven’t yet fully expanded. We believe it is in the genus Apantesis which is pictured on BugGuide.