Nature Nearby: Nature’s winter forecaster?

The woolly bear caterpillar, or Pyrrharctia isabella, is the larval form of the Isabella tiger moth.

BY FRED SEITZ — Walking down the street on a mild October afternoon, my wife and I encountered one of winter’s most famous and visible harbingers, a banded woolly bear caterpillar (aka woolly worm or fuzzy worm). Pyrrharctia isabella is the caterpillar, or larval form, of the Isabella tiger moth. The pudgy little fellow was hurrying across the street in a northerly direction. Folklore would say that its northerly movement foretells a mild winter (we’ll see). Others would maintain that the relatively wide black band on this passerby predicts a severe winter.  

While some of us may want to believe that his northerly travel will prevail as an indicator of an easy winter, it’s more likely he (or she) was merely looking to find a safe place to burrow into for the approaching season: the ground, a rotted log or between some rocks.

And our little friend has one up on General Motors. Mom Nature has equipped these caterpillars with natural antifreeze, which can protect them down to minus 90 degrees Fahrenheit. When spring returns, the caterpillar will awaken, emerge from a cocoon, and then metamorphize into an approximately 2-inch-wide yellow-winged moth.

The belief that the woolly bears’ coloring is related to the severity of winters became famous following a multi-year study started in 1948 by Dr. Howard Curran, curator of entomology at the American Museum of Natural History in New York City. Curran collected woolly bears and compared widths of their bands in an effort to study the old American weather wisdom. While the study was small and full of limitations, the research inspired and preserved the tradition of looking for, and sometimes collecting, these pre-winter wanderers in many parts of the U.S. and Canada. Woolly bear festivals are even held in a number of states to support this tradition. For example, the annual Dick Goddard Woollybear Festival is held every fall in downtown Vermillion, Ohio, and includes a parade and an “official woollybear winter weather prediction based on the colors of the woollybear.” (At some of these festivals, speedy woolly bears can compete in woolly bear races and show off more than their bands.)

I have enjoyed watching these caterpillars since I was a child, but I would caution against collecting them with bare hands. While stories of them injecting venom through their bristles are false, the caterpillars’ bristles are spiky, and some folks’ skin may react to this roughness.

Perhaps enjoying their speedy motion and fuzziness from a distance is the best way to appreciate the woolly worm. Even if they’re not good predictors of the coming winter’s severity, woolly bears remind us that winter, in all its uncertainty, is on the way.

Also, you wouldn’t want to take some bird’s or insect’s lunch.