Tag Archives: Woolly Bear

What Do Woolly Bear Caterpillars Eat?

Woolly Bear.JPGDid you ever wonder?

The Woolly Bear Caterpillar, the larval stage of the Isabella Tiger Moth, can be spotted all over the place on the East Coast this time of year. Like most insects except the Monarch, they will spend the winter here in a hibernation-like state called diapause. Many species of butterfly and moth actually spend the winter tucked into their chrysalis. The Woolly Bear is spotted out a bit later in the season perhaps in part because it actually spends the winter in caterpillar form, with a special anti-freeze inside of it that will keep it from forming ice crystals inside its body. Continue reading


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Filed under caterpillars

Arctic Woolly Bear Caterpillar

Having received a Field Guide to caterpillars this Christmas, I have been learning a lot. Appropriately for the season, my focus was drawn to a chill-oriented dude.

I was surprised to learn that the longest lived caterpillar on record is the Arctic Woolly Bear at 22 years! Like its cousin the Woolly Bear,  it spends the winter as a caterpillar frozen through (described here). However while Woolly Bears in Maryland thaw, pupate, and emerge as the Isabella Tiger Moth in the spring, the Arctic Woolly Bears spend another brief cold “summer” as a caterpillar, and routinely freeze over for 14 more winters before one summer they finally pupate and reproduce and die all in about 24 hours. Sounds more intense than senior prom as far as expectations for virginity loss.
But I will not go on about this when this amazing video from Discovery’s Frozen Planet will show and tell you more, and in an accent far posher than mine. All you have to do is click.

Image (Still of frozen caterpillar stolen from film).



Filed under Insects!

What Does the Woolly Bear Turn Into?

Preview answer for the impatient: this.

Isabella Tiger Moth

Ok, I promise you I have interests beyond caterpillars and trees. Believe me, lack of interests is not a problem for this girl. But today is another note on our metamorphosizing friends.


This happens to be the only photo I’ve taken of a Woolly Bear. It is a reminder of the reason insects need to reproduce in such large numbers. Their trophic level is not indeed an enviable one. And I’m pretty sure the cars kill more of them than the predators.

With the sudden onset of legit cold weather in Maryland, overwintering is on my mind. How to make it through the dreary blustery days? For a contemporary US human, there is indoor heat, which I appreciate because my metabolism does not, to the best of my knowledge, get down with the hibernation status/slow heartbeat/sleep until spring thing. Humans evolved in Africa (/the garden of Eden either way) and it was warm there. This chilly shizz does not come natural. For winters immemorial our opposable thumbs have gotten busy chopping firewood, laying brick, stuffing rags into cracks in the cabin, and more recently tapping our touch screens to turn up the thermostat.

But the insects have to face the elements head on and thumbless, which has led to some pretty elaborate measures. Monarchs migrate 1000s of miles to where the weather suits their clothes (hey Baby) and there is a Spicebush Swallowtail butterfly chrysalis overwintering in my backyard. But what of the Woolly Bear? This caterpillar, frequently spotted every time I go outside these days (usually crawling into the path of a car) is out pretty late relative to its sensitive cousins.

Allegedly a blacker bear is a sign that the winter will be colder. Also allegedly this is based on a very small sample size and not reliable.

I have recently learned that this friend is planning to overwinter… AS a CATERPILLAR. That sounds rough to me but hey, at least they come woolly and will not have to ask Santa for some SmartWool long underwear from REI. That would be expensive. Now they are looking for the right log to snuggles up in all winter long. I guess that requires a lot of high-risk exploration despite the threat of the ever so popular automobile.

According to Wikipedia these dudes wait until it is fall to hatch from their eggs in their familiar larval form. They eat a wide variety of native plants- not a picky gluten-free kind of insect. For once geez. Then it is time to find the cozy overwintering locale. Once there the Woolly Bear’s heart stops, its gut freezes, then its blood freezes, and then everything else ices over so that the caterpillar is FROZEN SOLID. Wow.

When the spring rolls around and the Woolly Bear thaws out, he forms a pupa and emerges shortly thereafter in the form of the Isabella Tiger Moth. A yellow/brown guy meant more to blend in than stand out. I’m not sure if I’ve seen one outside or not. You know all those moths they look alike. Or maybe I am just blind to their individuality. Google for yourself and see.

Here is another Moth image from Google Images (hard to find them outside right now…)

Isabella Tiger


The arctic cousins of these Bears go through a similar process, freezing and thawing, but over the course of 14 YEARS before they finally turn into a beautiful moth, finds a partner, makes the babies, and dies in a few short days. I have blogged more about this craziness here.


Filed under Insects!, Seasons