Woolly Bear Wisdom was originally published in the BFEC Newsletter, Vol. 14/No. 4, Fall 2010.
Fall seems to be a busy time for caterpillars, especially for the woolly bear, which can hardly be bothered to pause while crossing your path. Don’t take it personally — it is surely, single-mindedly, en route to more food before cold weather signals that it’s time to hibernate.
The common woolly bear caterpillar is the immature form of the Isabella tiger moth (though it has many look-alike cousins). They are black with a rust-colored band in the middle, and their stiff bristles give them a fuzzy appearance. The caterpillar survives the winter in hibernation by producing a chemical that works much like antifreeze, keeping its body tissue from freezing. In spring it matures into the moth, which is dull yellow-orange with a few black spots.
Now for the question we’ve all been waiting for: does a greater proportion of black on the woolly bear actually predict a harsher winter? Unfortunately for the believers of the folklore, caterpillars born in the same clutch can vary widely in color and rust-colored bands expand over time as caterpillars mature. Even if they can’t predict its severity, their hurried appearance in the fall is a true sign that winter is coming.