Wooly Bears? A Common Fall Sight
By Marilyn Shy, Kalkaska Conservation District
I think most people have seen the fuzzy brown and black caterpillars crawling along the surfaces of leaves, sidewalks and bare ground in the fall, known in the Midwest as “wooly bears.”
But have you heard the stories about how these creatures can predict the weather?
The wooly bear caterpillars, also called wooly worms in the southern U.S, have long been used to foretell the severity of the upcoming winter. If the rusty brown band in the middle of their bodies is wide, it was thought that was a sign of a mild winter. If it was narrow, and the black bands on their front and back sides were wide, that indicated a more severe winter. But how did this legend develop?
The story goes like this: In 1948, Dr. C.H. Curran, curator of insects at the American Museum of Natural History in New York City, took his wife on a trip in the fall to Bear Mountain State Park, 40 miles to the north. Dr. Curran collected as many wooly bears he could in a day, determined the average size of the reddish-brown middle segment on each caterpillar and attempted to forecast the coming winter. He continued this experiment for the next 8 years. Since the middle bands he found took up more than a third of the caterpillars’ bodies, and the corresponding winters were milder than average, he determined the folklore had some merit.
But Curran knew his data samples were small, and it was really just an excuse for having fun. Curran, his wife and friends escaped to Bear Mountain each fall and began calling themselves The Original Society of the Friends of the Wooly Bear.
Thirty years after the last meeting of the Society, the nature museum at Bear Mountain resurrected the counts and the winter forecasts. These have continued more or less tongue in cheek, since then. Other counts and festivals abound. In Banner Elk, North Carolina, there is the Wooly Worm Festival every October, and in Vermillion, Ohio there is the annual Woolybear Festival in the same month.
Although most scientists discount the wooly bear weather predictions, Mike Peters, an entomologist at the University of Massachusetts says there could be, in fact, a link between winter severity and the brown band of the wooly bear. “There’s evidence that the number of brown hairs has to do with the age of the caterpillar----in other words, how late it got going in the spring. The [band] does say something about a heavy winter or an early spring. The only thing is… it’s telling you about the previous year.”
The wooly bear caterpillar is the larval form of the Isabella Tiger Moth, which has beautiful yellow-orange and cream- colored wings spotted with black. It’s common from northern Mexico throughout the United States and across the southern third of Canada. There are two generations of the caterpillar each year. The first appear in June and July, the second in the fall in September and October. The caterpillars are most active during the day, searching for food such as violets, lambsquarters, and clover. After filling up in the fall, the caterpillars look for a place to spend the winter, under bark, or inside cavities of rocks or logs. Their entire body enters a “frozen” state until May, when it spins a cocoon and transforms into the Isabella Tiger Moth.
Each year, the wooly bears look a bit different. So if you come across a wooly bear this fall, observe the colors of the bands, and have some fun guessing what they foretell about the coming winter (or what they confirm about the recent past winter and spring!)