Science: Wooly Weather Prophet

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In the spring, a young man's fancy; in the fall, woolly bear caterpillars have a brown band in their midriffs. If the brown band is wide, it will be a mild winter. If the brown band is narrow, the winter will be a freezeroo. So countrymen in the northeastern states have believed.

A year ago, Dr. C. Howard Curran, curator of insects and spiders at New York's American Museum of Natural History, took a look at the woolly bear caterpillars and noted that they all had narrow bands. Sure enough, along came last winter's big snow and ice storms. Curran decided to take another look at woolly bears.

Last week, on slopes above the Hudson River, Curran and a pack of entomologists hunted woolly bear caterpillars (larvae of a tiger moth, Isia Isabella) and measured their waistbands. In 15 specimens, they averaged five and one-third brown segments. Last year, said Curran, they averaged less than three. Does that mean a milder winter ahead?

If the woolly bear forecasting proves to be no good, Curran will have to figure out what actually causes the annual variations in the caterpillars' cummerbunds. And if it is accurate, why?