These remarkable creatures come fully equipped with a unique seasonal superpower. Woolly Bears nearly freeze solid during hibernation. Their bodies produce a chemical called a cryoprotectant that acts like anti-freeze to protect their organs and body tissues from being damaged from the cold. Some will endure the entire winter completely frozen, only to come awake during the spring, spin a fuzzy cocoon and transform into the Isabelle Tiger Moth. Amazing!
This natural defence is why the woolly worm has become the centre of folklore—as a weather prognosticator. Covered in thick, fluffy-looking hair (which is actually quite stiff), the Woolly Bear sports bands of black and reddish-brown. An age-old mythology suggests that the size of the brown band on these critters may serve to predict the severity of the coming winter: the wider the brown band, the milder winter will be, and the more black there is, the more severe the winter. Others have suggested that the 13 segments of the Bear’s body correspond to the 13 weeks of winter.
I think stories like these are a great way to engage children about the wonders of nature. Science, of course, tells us that the caterpillar’s colour is more closely related to the growing season—the better the season is, the more it eats and the bigger it grows, and that these caterpillars will shed their molt at least six times before reaching adult size.
In fact, the Woolly Bears that we see in the autumn are the second generation. The first emerge in April, feed, spin a cocoon of silk and then after pupating for two weeks, the Isabelle Tiger Moth emerges. Fertilized females then lay eggs on trees and grasses, and new caterpillars hatch to begin the cycle again.
The Bears are gentle creatures, their minute bristles do not sting, and their bodies are not poisonous. While they do eat the leaves of some tree species including maples and birches, there is never a large enough population to have a significant impact on foliage; they simply add another dimension to the autumn landscape and yet another sensory offering from a season that is an overwhelming offering of awesome.
Oh, and one more thing!
Should you spot a Woolly Bear in the winter, please resist touching them… the heat from your hand could actually cause a thaw and awaken them, to their ultimate peril.