The woolly bear caterpillar—with its 13 distinct segments of black and reddish-brown—has the reputation of being able to forecast the coming winter weather.
Here are the history, facts, and lore about this legendary caterpillar.
How the Woolly Bear Became “Famous”
- In the fall of 1948, Dr. C. H. Curran, curator of insects at the American Museum of Natural History in New York City, took his wife 40 miles north of the city to Bear Mountain State Park to look at woolly bear caterpillars.
- Dr. Curran collected as many caterpillars as he could in a day, determined the average number of reddish-brown segments, and forecast the coming winter weather through a reporter friend at The New York Herald Tribune.
- Dr. Curran’s experiment, which he continued over the next eight years, attempted to prove scientifically a weather rule of thumb that was as old as the hills around Bear Mountain. The resulting publicity made the woolly bear the most recognizable caterpillar in North America.
- Read more articles about fun ways to predict the weather.
What is the Woolly Bear?
The caterpillar Curran studied, the true woolly bear, is the larval form of Pyrrharctia isabella, the Isabella tiger moth. See and share this picture of a woolly bear!
Here is more background:
- This medium-size moth, with yellowish-orange and cream-colored wings spotted with black, is common from northern Mexico throughout the United States and across the southern third of Canada.
- As moths go, the Isabella isn’t much to look at compared with other species, but its immature larva, called the black-ended bear or the woolly bear (and, throughout the South, woolly worm) is one of the few caterpillars most people can identify.
- Woolly bears do not actually feel much like wool—they are covered with short, stiff bristles of hair.
- In field guides, they’re found among the “bristled” species, which include the all-yellow salt marsh caterpillar and several species in the tiger moth family. Not all are ‘woolly bears!’
- Woolly bears, like other caterpillars, hatch during warm weather from eggs laid by a female moth.
- Mature woolly bears search for overwintering sites under bark or inside cavities of rocks or logs. (That’s why you see so many of them crossing roads and sidewalks in the fall.)
- When spring arrives, woolly bears spin fuzzy cocoons and transform inside them into full-grown moths.
- Typically, the bands at the ends of the caterpillar are black, and the one in the middle is brown or orange, giving the woolly bear its distinctive striped appearance.