The Woolly Bear Weathermen
Published: October 14, 1992
Though appealingly fuzzy, it hardly makes a fashion statement: two bands of black and one of brown, the comfortable brown of a beloved sweater. After a summer spent munching grass and leaves, the woolly bear caterpillar is walking now -- all over country roads, across decks and patios, around stone walls and piles of wood.
Isia Isabella, as the scientists call it, will walk until it finds a cozy place to take its winter nap. With the spring's warmth it will wake up and pupate, spinning a cocoon out of its fuzz fortified with a few squirts of silk.
Two weeks later, the big metamorphosis complete, it will make its debut as an unremarkable moth: yellow-brown wings with black dots.
If common and dull, the woolly bear caterpillar is also benign and peaceful. It causes no real trouble for farms or woodlots; no one considers it a pest, and it has little to fear from birds, who find its fuzz unappetizing. What makes it remarkable is that for centuries now, people have turned to it to forecast the weather.
As the leaves turn color, nature watchers check the woolly bear's bands of fuzz. The broader the black bands, they say, the colder will be the coming months. Since Colonial times, Americans have gauged the bands as they stocked their larders and gathered fuel for the winter.
Scientists say the woolly bear caterpillar's stripes are worthless predictors, pointing to research that found no relationship between them and winter temperatures. But the fascination of the woolly bear weathermen endures. By the time real winter sets in next January they will be curled away, fast asleep and nowhere to be found. How cold is it? How wide were those black bands? No one will remember.
Photo of Isia Isabella, or woolly bear. (John Serrao/Photo Researchers)