KENTUCKY (FOX 56) — The woolly bear caterpillar, also known as the woolly worm, has been the center of an old wives tale for predicting the weather for centuries.

To set the record straight, the woolly worm isn’t actually a worm. They’re the larvae of the Isabella tiger moth! In terms of appearance, these caterpillars have 13 distinct variations of either rusty brown or black markings, according to the Old Farmers Almanac.

According to the legend, the browner the caterpillar is, the milder the winter will be. The more black markings there are, the more of a harsh winter is coming.

However, if you come across an all-black or all-white caterpillar, be assured that an apocalyptic winter isn’t coming. These are different species of caterpillars and have not been historically used for weather prediction.

History of the Woolly Worm

According to the Old Farmer’s Almanac, a man named Dr. C.H. Curran, curator of insects at the American Museum of Natural History in New York City, put the myth to the test. He collected as many woolly worms as he could to determine a trend in their markings. He continued this study over the next eight years.

Between 1948 and 1956, 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 worm’s body.

This would predict a milder winter. The corresponding winters turned out to be milder than average, and Curran concluded that the folklore has some merit.

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But many scientists discount the folklore of woolly bear predictions as just folklore. According to the Old Farmer’s Almanac, Mike Peters, an entomologist at the University of Massachusetts, doesn’t disagree, but he says there could be a link between winter severity and the brown variations of a woolly worm caterpillar.

“There’s evidence,” Peters said, “that the number of brown hairs has to do with the age of the caterpillar — in other words, how late it got going in the spring. The [band] does say something about a heavy winter or an early spring. The only thing is … it’s telling you about the previous year.”

How to “read” the Woolly Worm

The first step is that you need your own woolly worm. These critters emerge in two generations each year, the first appearing in June and July and the second in September. September woolly worms are the ones who come to be known as the “weather prophets.”

Much like the weather, woolly worms vary. Every year, the woolly worms look different, and it depends on the region they’re found in.

The rule of thumb for predicting the winter via woolly worm is the ratio of its colored markings. If the rusty band is wide, there will be a mild winter. The more black there is, the more harsh the winter will be.

Kentucky’s 2023 Woolly Worm Prediction

FOX 56 surveyed viewers in central Kentucky on the variety of woolly worms they’ve come across this year.

A grand total of 91 woolly worms were submitted. However, 54 of them weren’t woolly worms at all. Thirty-eight all-black and 16 solid-white caterpillars were submitted and mistakenly predicted a severe winter. Luckily, that may not be the case.

Out of the 37 eligible woolly worms, here’s what we gathered:

  • 58% of Kentucky’s woolly worms predict a mild winter
  • 38% of Kentucky’s woolly worms predict a moderate winter
  • 2% of Kentucky’s woolly worms predict a harsh winter

However, if Peters is correct, these findings would be indicative of the winter of 2022.

FOX 56’s Weather Authority reported in March 2023 that the 2022—23 winter season was one of the warmest winters in almost a century. Snowfall was nearly 8 inches below normal, and December, January, and February came to a close with temperatures above average. 2022—23 was the second warmest winter, just 1.3 degrees behind 1931—32’s record of 43.9 degrees.

Whether their predictions have any merit, there’s no way to truly know. But their legacy has withstood the tests of time, and Kentuckians continue the tradition to this day.