Posted 10-01-2003 at 04:55:00
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From the Old Farmer's Almanac:
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. The woolly bears' variable bands, made up of 13 distinct segments of black and reddish-brown -- and their reputed ability to forecast the severity of the coming winter -- had long fascinated the entomologist.
Dr. Curran proposed a scientific study. He 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. His 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 famous and most recognizable caterpillar in North America.
The caterpillar Curran studied, the true woolly bear, is the larval form of Pyrrharctia isabella, the Isabella tiger moth. 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 some of the other 11,000 species of North American moths, 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 by name.
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. Doug Ferguson, an entomologist at the National Museum of Natural History in Washington, D.C., says, "I've heard people call different caterpillars 'woolly bears,' even ones that are all black, all brown, yellow, or gray. It's the hairiness they're referring to. I guess you'd better be careful about which caterpillar you're looking at before you make your prediction."
Woolly bears, like other caterpillars, hatch during warm weather from eggs laid by a female moth. After feeding on dandelions, asters, birches, clovers, maples, weeds, and other vegetation, mature woolly bears disperse and 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. According to legend, the wider that middle brown section is (i.e., the more brown segments there are), the milder the coming winter will be. Conversely, a narrow brown band is said to predict a harsh winter.
Between 1948 and 1956, Dr. Curran's average brown-segment counts ranged from 5.3 to 5.6 out of the 13-segment total, meaning that the brown band took up more than a third of the woolly bear's body. As those relatively high numbers suggested, the corresponding winters were milder than average. But Curran was under no scientific illusion: He knew that his data samples were small. Although the experiments popularized and, to some people, legitimized folklore, they were simply an excuse for having fun. Curran, his wife, and their group of friends, who called themselves The Original Society of the Friends of the Woolly Bear, escaped New York each fall for the glorious foliage and the meals at the posh Bear Mountain Inn. The naturalist Richard Pough was a member, as was Kim Hunter, the actress who starred in the movie Planet of the Apes.
Thirty years after the last meeting of Curran's society, the woolly bear brown-segment counts and winter forecasts were resurrected by the nature museum at Bear Mountain State Park. The annual counts have continued, more or less tongue in cheek, since then. This fall, museum director Jack Focht will gather a dozen or so caterpillars, as he has done since 1988, and spread them out on the kitchen table of his "folklore consultant," Clarence Conkling. The two men will count the brown segments, average them, and declare another forecast from Woolly Bear Mountain. "We're about 80 percent accurate," he says.