Banded Woolly Bear Caterpillar

I Can’t Make Heads or Tails of It

A Banded Woolly Bear, caterpillar form of an Isabella Tiger Moth.
A Banded Woolly Bear, caterpillar form of an Isabella Tiger Moth.


The Banded Woolly Bear Caterpillar is found in temperate regions of North America. It emerges from the egg in the fall and overwinters in its caterpillar form, when it literally freezes solid. It survives being frozen by producing a cryoprotectant in its tissues.  Because the summer period for vegetative growth and hence feeding is so short in some northern areas, the Woolly Bear can feed for several summers, freezing again each winter before finally pupating. Some are known to live through as many as 14 winters in the Arctic. Once it emerges from its pupa as an Isabella Tiger Moth it has only days to find a mate before it dies.


Folklore About the Banded Woolly Bear Caterpillar

Folklore of the eastern United States and Canada holds that the relative amounts of rust and black on a Woolly Bear caterpillar are an indication of the severity of the coming winter. It is believed that the narrower the rust colored band in the middle of the Woolly Bear caterpillar is in the fall, the more severe the winter will be. In reality, hatchlings from the same clutch of eggs can display considerable variation in their color distribution, and the rusty band tends to change width with age.