photo by Richard Seaman

Name: Isabella Tiger Moth/Banded Woolly Bear

Classification: Pyrrhactia isabella

Location: Anywhere very cold, including the Arctic

I discovered this caterpillar on Frozen Planet with Sir David Attenborough, and found myself fascinated. When the Arctic winter comes, the caterpillar literally freezes solid, the cryoprotectant in its cells allowing it to live through the cold. First its heart stops beating, and then its gut freezes, and its blood, shortly followed by the rest of its body. Every summer it defrosts in order to feed, before freezing again. After fourteen years of this, it pupates becoming a moth (below)


image by Wikipedia

After pupating, it has only one day to find a mate and breed before dying. I think this life cycle is so far out of the ordinary to anything we know that lives in more temperate conditions, and I find it hugely interesting. Truly the world is an amazing place.


**The above pictured is actually the larva of a Giant Leopard Moth / Eyed Tiger Moth - Hypercompe scribonia - which is in the same family of moths (Arctiidae) than the Isabella Tiger Moth described below…

Banded Woolly Bear caterpillar (of the Isabella Tiger Moth) - Pyrrharctia isabella - early instar stages exhibit mostly black coloration with an orange band developing larger for each subsequent molt.  During the final larval stage, the caterpillar will typically appear all orange with no black remaining.

The absence of orange is said to predict a harsh winter, while a large orange band is telling of a mild winter ahead.  This prediction method may work in the sense that the caterpillars will be forced to hibernate if the temperature drops.  The sooner they are forced into hibernation, more early instar stages will be observed in the wild (more black, less orange); the sooner the temperature drops, the more likely it may be a harsh winter.

Friends of Woolly Bear Caterpillars and Winter Weather Predicting

Woolly Bear Caterpillars and Winter Weather Predicting


I have written before about the “signs of winter” that are part weather folklore and part science. Those posts have touched on the a caterpillar known as the woolly bear (the larval form of Pyrrharctia isabella, the Isabella tiger moth) being seen as a winter weather indicator.

I did some further digging on a recent cool summer night that felt more like autumn to see how…

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