What’s
black and brown, fuzzy, and curls in your hand when it’s picked up? You guessed it—a woolly bear
caterpillar! The larval form of the
Isabella Tiger Moth, Pyrrharctia isabella, also known as the woolly bear
or woolly worm caterpillar, is found in northern Mexico, throughout the US and
the southern third of Canada. There are
even reports of these moths being found in the arctic!
This
extraordinary species lives for a whopping 14 years beginning in an egg,
where woolly bears will spend up to two weeks before hatching in either May or
August. Once freed from their eggs, the hungry
little caterpillars begin to eat… everything! Woolly bears are considered generalists,
meaning they will consume a variety of leafy plants, including herbs, shrubs,
and trees! In contrast to this, the
monarch caterpillar is a specialist, primarily feeding on milkweed plants,
which give the monarchs their toxicity. Unlike
monarchs, woolly bears are not toxic and, therefore, are not aposematic—they don’t
sport bright colors and patterns associated with the warning signals of toxicity
like monarchs do.
Although
woolly bears can be found throughout the summer, they are more commonly
observed in the fall as the August generation travels across paths and roads
seeking a good over-wintering hideout. These
little guys find refuge in places such as logs, under bark, and in rock
cavities, which help protect them from the bitter cold of winter. Additionally, woolly bears have a unique
quality to their physiology that allows them to freeze solid throughout the
winter and survive to thaw in the spring!
In fact, these caterpillars can survive in -76oF temperatures! How, you ask?
Well, this species is one of many that produces a kind of antifreeze in
their tissues called a cryoprotectant. This compound effectively lowers the freezing
point, allowing the caterpillars to survive extremely cold temperatures, even after
becoming a woolly bear-sicle!
The
woolly bear carries on this ‘start and stop’ life cycle for most of its life,
molting each year, until it finally garners enough resources to form a fuzzy
brown cocoon in the spring. After spending
a month in their cocoons, they transform into pupas (a process known as
pupation) and emerge as beautiful orange moths!
Then the race is on and the woolly bear moths have 24 hours to track
down a mate and lay eggs before their life cycle finally comes to an end and they
die. As a moth, woolly bears are so
driven to fulfill their niche, they don’t eat a bite during this stage of life!
Did you know woolly bears are famously
known to predict the weather! Well,
almost. From 1948 to 1956, Dr. C.H.
Curran—then, the curator of insects at the American Museum of Natural History
in New York City—began experimenting with woolly bears. Each year, Curran collected woolly bears and
counted their segments, noting the number of segments with spiny black hairs
and those with brown. Woolly bear caterpillars
have 13 segments in total and around a third of them make up the rust-colored
band in the middle, which widens when woolly bears molt. If, on average, the woolly bears had more
black on them, he predicted the coming winter would be horrendous. However, if, on average, the caterpillars were
more brown than black, Curran predicted a milder winter. After making his predictions, he reported
them to a friend at the New York Herald Tribune, who incidentally published Curran’s
winter forecast in the paper, which is why woolly bear caterpillars are one of
the most recognizable in the country, next to monarch caterpillars! After eight years of counting, predicting,
and analyzing winter weather results—Curran is said to admit that there just might
be something to this old tale!
So,
the next time you see a woolly bear caterpillar crossing the road, help it to
the other side and take note of its coloration—was its brown band wide or
narrow? Were you able to forecast the
winter weather accurately? Let us know in the comments below!
It's a HOOT--The Animal Joke of the Week!
Q: What did the judge say when the skunk walked into the court room?
A: Odor in the court!
Riddle Me This...
I can fly, I can walk, and I can swim but I don't get wet. What am I?
(A: wodahs s'drib a)
Phenomenal Phenology!
Here's what's happening this week:
- Red foxes begin mating
- Canada geese begin to arrive
- Beavers begin mating
Critter Corner!
Here's an easy one... this will get you warmed up for next week's challenge!
That's all for this week!
Stay wild & free & healthy as can be!
-CT
