Woolly worms: weather predictor or silly legend?

Matthew Lane • Oct 27, 2019 at 6:00 PM

KINGSPORT — Now that the sweltering days of summer are behind us, it’s probably time to start talking about how cold it’s going to be this winter.

But forget about checking the National Weather Service and put down the Old Farmer’s Almanac. Just go outside, track down a fuzzy little woolly worm and take a close look at how brown its bristly back is.

That should give you a good idea how cold and severe this winter is going to be.

Or not.

The Times-News spoke with two local park rangers about the woolly worm and its ability to predict the upcoming winter season. Both men enjoyed talking about the legend behind the worm (it’s actually an Isabella tiger moth caterpillar), but neither one puts much stock in the critter’s weather prognostication.

“It’s fun, interesting folklore, but how much truth is there to it? I’m not so sure,” said Marty Silver, park ranger at Warriors Path State Park.

“I get that question on occasion, but not too often,” said Bob Culler, park ranger at Bays Mountain Park. “I tell folks they’re better off checking the long range forecast from the weather service. As for the almanacs, those forecasts are made in advance and are about as accurate as the woolly worms are.”


How the woolly worm became famous and seemingly able to predict the upcoming winter season dates back to the fall of 1948, when Dr. C.H. Curran, a curator of insects at the American Museum of Natural History in New York City, took his wife to Bear Mountain State Park to study the woolly worm caterpillars.

Woolly worms have 13 distinct segments — apparently one for each week of winter — with each segment either being brown or black. As the legend goes, the more black the worm is, the colder the winter. A browner worm means a milder winter.

And if you happen to see an all black or all brown woolly worm, ignore it. It’s not even a woolly worm, but another species entirely. Actual woolly worms will have some amount of black and brown and not be just one color.

Curran collected a number of caterpillars, determined the average number of reddish-brown segments, and forecast the coming winter weather through a reporter friend at The New York Herald Tribune. This experiment continued for eight years in an attempt to scientifically prove a weather rule of thumb that was as old as the hills around Bear Mountain.

Needless to say, the legend stuck and continues to this day.


Woolly worms should be out and about now. You’re able to see them more beginning in October and continuing into November. The caterpillars are moving into areas where they can burrow down under dead logs and rocks for the winter season and emerge as moths next spring.

Each one is different. Even in the same year with the same weather, they’re not going to be exactly the same, Culler said.

“The ones I’ve seen this year have been equally balanced between brown and black, so if you believe the old stories we’ll have as much warm weather as cold,” Silver said. “I’m not a climatologist and a lot of the old weather signs are based on years of observation, but also a lot of hope and wish and most signs in nature are not an indication of what’s going to be but of what’s been.”

Meaning the woolly worm might be telling us more about the summer of the past than the winter of the future.

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