A woolly-bear that I that rescued, on the 10th of October, as it tried to cross the road. Unfortunately, there were several nearby woolly bears that hadn’t survived their trip across the two-lane. Photograph by the Author.
I know that “Fuzzy Wuzzy was a bear” and not a woolly bear, but I couldn’t resist – Author’s Note
Do
woolly bears predict the weather? Are
they weathermen? That is what the legend
says, anyways. Did you ever wonder if
the myth was true? I did, and here is
what I found out.
Woolly
bear, black-ended bear, fuzzy bear, woolly worm, hedgehog caterpillar, it
doesn’t matter what you call them, these are all names for the same thing, the
caterpillar form of the isabella tiger moth (pyrrharctia isabella). Woolly bears are bristly and black on both
ends with an orange or rusty-brown middle, and if you pick them up, they will
curl into a tight ball and play dead, which is why they are sometimes called hedgehog
caterpillar. You commonly see them, at
least in the Northeast United States in early autumn, as they search for a
dark, dry, sheltered place, like a pile of leaves, or under some bark, a rock
or a log, to hibernate for the coming winter.
By the way if they are not black and rust colored and instead are all
black or black and some other color then they are not a woolly bear caterpillar
but are something else instead1.
A giant leopard moth caterpillar found in Minister Valley, Pennsylvania, on October 30, 2020, photograph from the Katie Reynolds collection, used with permission.
Each
fuzzy 1½ inch (3.8 cm) long woolly bear becomes an isabella tiger moth, which
is an orange-yellow moth with a wingspan of 1½ to 2 inches (or 3.8 to 5 cm) and
a body that is spotted with rows of black dots running up and down the
body. Isabella tiger moths are commonly
seen at night throughout the summer.
Woolly bears feed upon a variety of plants and weeds, like dandelions, plantains,
nettles, violets, lamb’s quarters, and clover.
Insect experts note that there are two generations of woolly bears each
year, one generation appearing in June and July and the second one in
September. It is the second generation
of woolly bears that according to folklore can foretell the coming winter
weather.
“Pyrrharctia isabella – Isabella Tiger Moth”, photograph by Andy Reago and Chrissy McClarren, “Pyrrharctia isabella – Isabella Tiger Moth”, August 4, 2014, HERE.
According
to folklore common throughout the Midwest and Northeast United States, the bristles
on woolly bear caterpillars can predict how bad the coming winter will be. Woolly bears are covered in black bristles on
their front and rear and with rusty-brown bristles upon their middles and
according to the myth, the wider the bands of black fuzz on the woolly bear,
the harder, colder, snowier and more severe the coming winter will be. If the bands of black fuzz are narrow and the
middle band of rusty-brown fuzz is wide, then the winter will be mild, with
less snow and cold. And finally, traditional
forecasters say that since woolly bears have thirteen segments, which
correspond to the thirteen weeks of winter, if the black band on the rear of
the caterpillar is larger than the front, then the second half of the winter
will be worst and if the black band on the front of the caterpillar is the
largest then the first half of winter will be the worst.
A woolly bear found in Minister Valley, Pennsylvania, on October 30, 2020, photograph by the Author.
This
myth has existed since the late 18th and early 19th
centuries. However, it didn’t become
popular until Dr. Howard Curran, the curator of entomology, at the American
Museum of Natural History, in New York City, conducted a study on woolly bears
and weather during the fall of 1948. He
examined 15 woolly bears that he collected in Bear Mountain State Park, 40
miles north of New York City, counted the number of rusty-brown segments and
then made a prediction about the coming winter.
His prediction was printed in the New York Herald Tribune where it was
picked up by the national press and the rest is, as they say, history! Dr. Curran continued his experiment over the
next eight years, until 1956, in an attempt to scientifically prove the old
wives’ tale about woolly bears and winter weather prediction2.
Unfortunately,
woolly bears can’t predict future winter weather. The length of a woolly bear’s rusty-brown
middle section is an indication of how long and how well the caterpillar has
been feeding and on how old it is. The
better the spring and summer growing and feeding season, the bigger the
caterpillar will be and the narrower its middle rusty-brown section will
be. Also, the width of the woolly bears
rusty-brown mid-section shows its age, because the caterpillars shed their skin
and molt six times before reaching their full adult size. With each molt, a wooly bear becomes less
black and more reddish-brown. So, really
the amount of orange-brown on a woolly bear just tells us about the weather of
the past several months and has nothing to do with what the coming winter
weather!
So,
if the color of the woolly bear bristles can’t tell us what the future winter
will be, what do they do? The bristles,
or setae, help the caterpillar freeze solid more comfortably and survive the
freezing cold winter. During hibernation
woolly bears create glycerol, a natural, organic antifreeze. Woolly bears will freeze until all but the center
of their cells are frozen. Woolly bears
can survive winter temperatures as low as -90oF (-68oC)
and have even been known to survive an entire winter frozen inside of ice3.
The woolly-bear that I that rescued, on the 10th of October, photograph by the Author.
So
next autumn, when you see a fuzzy wuzzy woolly bear crossing your path, you
will know that it isn’t a weatherman.
I
hope that you continue to enjoy The Woodsman’s Journal Online and look for me
on YouTube at Bandanaman Productions for other related videos, HERE. Don’t forget to follow me on both The
Woodsman’s Journal Online, HERE,
and subscribe to BandanaMan Productions on YouTube. If you have questions, as always, feel free
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announce new articles on Facebook at Eric Reynolds, on Instagram at
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That
is all for now, and as always, until next time, Happy Trails!
Notes
1
All black bristly caterpillars, doesn’t mean that a new Ice Age is coming, it
is just a caterpillar from a different species of moth. Giant leopard moth caterpillars (hypercompe
scribonia, formerly ecpantheria scribonaria), which is found across
the eastern half of the United States and Canada, look like a solid black
woolly bear. And if you see a woolly
caterpillar that is solid yellow color, you might think that the coming winter
is going to be very mild, when in fact what you are seeing is a yellow bear
caterpillar (spilosoma virginica), that can be found across the United
States, Canada and eastern Mexico.
From National Weather Service, “Woolly Bear
Caterpillar - Winter Predictor Or Not?”
2
Between 1948 and 1956, Dr. Curran’s research concluded that the average number
of rusty-brown segments of woolly bear caterpillars, ranged from 5.3 to 5.6 out
of 13 segments, which is more than a third of the length of the average woolly
bear, interestingly, between 1948 and 1956, the winters were milder than usual
around New York City. Dr. Curran, rather
tongue in cheek, concluded that there might be something to legend of the
woolly bear as weatherman. However, he
knew that his sample size was too small and his conclusions scientifically
invalid, and in the end his annual trip to the woods to look for caterpillars
was just a good excuse to get away from the city and look at the fall foliage!
From
Catherine Boeckmann, “Woolly Bear
Caterpillars And Weather Prediction, Do Woolly Worms Really Predict Winter Weather?”
3 National Weather Service, “Woolly Bear Caterpillar -
Winter Predictor Or Not?”
Sources
Boeckmann, Catherine; “Woolly Bear Caterpillars And Weather
Prediction, Do Woolly Worms Really Predict Winter Weather?”, September 21, 2020,
Old Farmer’s Almanac, [©2020 Yankee Publishing Inc], accessed October 16, 2020
National Weather Service, “Woolly Bear Caterpillar - Winter Predictor Or
Not?”, https://www.weather.gov/arx/woollybear, accessed October 16, 2020
Reago,
Andy and McClarren, Chrissy; “Pyrrharctia isabella – Isabella Tiger Moth”, August 4, 2014,
https://commons.wikimedia.org/wiki/File:Pyrrharctia_isabella_%E2%80%93_Isabella_Tiger_Moth_(14842796231).jpg, accessed December 2, 2020
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