Do woolly worms really predict the winter ahead?

Imagine yourself as a student on the campus of The Ohio State University. It’s a nice, sunny day outside. Students are walking to class, others are having conversation beside Mirror Lake, and in the distance, you see your entomology professor running around with a crazed look in his eyes while waving a comically-sized insect net.

Yes, the latter really happened. The man in question is known as the BugDoc, professor emeritus of entomology at The Ohio State University, Dr. David Shetlar. I had the pleasure of visiting with him recently to ask him something that bugs my brain every year at this time, no pun intended.

Old wives’ tales are something of a hobby for farmers in Ohio it seems, especially when it comes to predicting winter weather. Everything in the Lord’s creation is up for grabs when it comes to telling us how bad the upcoming winter will be. Whether its corn husk thickness, leaf amounts, or wool growth on sheep, something somewhere will tell us winter is coming.

That leaves one logical question for the BugDoc. Are the stories I’ve heard all my life about woolly worms predicting the weather really true?

“The true banded woolly bear is the larvae of a moth. Most caterpillars are either the larvae of a butterfly or a moth. Generally, the hairy ones are going to turn into moths,” Shetlar said. “The moths are actually called Tiger Moths. The moths themselves are highly collected by entomologists and amateur collectors because they usually have bright, striped markings on them so that’s where they get the name Tiger Moth. There’s a lot of these woolly bear caterpillars out there. People may see them in weedy fields. There’s a yellow woolly bear, a red woolly bear, and so forth. But the one that gets most of the notoriety this time of year is the banded woolly bear.”

The black, brown, then black again bands are supposed to reflect what the following winter will be like in length and intensity.

“The normal statement is that the length of the black is supposed to predict the strength or the severity of the winter, which I find is kind of interesting because the natural color bands of these is black at the front, brown in the middle, and black at the back. If I were really going to say that it would be a predictor, I would say that it ought to be brown in the front, black in the middle, and brown at the back. I think there are some local variations. There are some people who say it’s the brown in the middle that predicts the the winter. That would be more correct in terms of the timeline we’re talking about. But the reality is there were some entomologists who a few years ago that actually did some regional studies. What they find is that there’s a significant amount of variability, even within a population in the local region,” Sheltar said.”To give you an example, I had a person here in central Ohio send me a picture of a banded woolly bear that was mainly black in the front and a little tiny narrow brown band in the middle and mainly black at the back. He said, ‘Boy this one’s predicting a harsh winter.’ But then I returned and said well here are two of the caterpillars that one of the local weathermen and I collected. And it had just a bare hint of black at the front, which meant there would be an early cold snap. I think we’ve already had that. And then it had almost two thirds of the body was brown, which means it’s going to be a long mild winter. And then another little black band at the end which means there would be a late cold snap in the spring time. And I said, ‘My woolly bear’s not predicting what your woolly bear is predicting.’ Especially since they were collected in the same county, that seems a little bit odd.”

Here is a summary of the legend from the National Weather Service Forecast Office out of La Crosse, Wis. that appeared in a former article.

According to folklore, the amount of black on the woolly bear in autumn varies proportionately with the severity of the coming winter in the locality where the caterpillar is found. The longer the woolly bear’s black bands, the longer, colder, snowier, and more severe the winter will be. Similarly, the wider the middle brown band is associated with a milder upcoming winter. The position of the longest dark bands supposedly indicates which part of winter will be coldest or hardest. If the head end of the caterpillar is dark, the beginning of winter will be severe. If the tail end is dark, the end of winter will be cold. In addition, the woolly bear caterpillar has 13 segments to its body, which traditional forecasters say correspond to the 13 weeks of winter.

“As with most folklore, there are two other versions to this story. The first one says that the woolly bear caterpillar’s coat will indicate the upcoming winter’s severity. So, if its coat is very woolly, it will be a cold winter. The final version deals with the woolly bear caterpillar’s direction of travel of the worms. It is said that woolly bears crawling in a southerly direction are trying to escape the cold winter conditions of the north. On the other hand, woolly bears crawling on a northward path would indicate a mild winter.”

The winter weather predicting abilities of the woolly bear have been the source of discussion since colonial times, but got a boost when C.H. Curran, the curator of insects at the American Museum of Natural History in New York, took a more scientific look at the legend in 1948. Curran examined autumn woolly bears in Bear Mountain State Park and applied the theory to make a winter weather prediction. He repeated the experiment for eight years and, with the help of publicity in The New York Herald Tribune, the fuzzy caterpillar was made famous.

But why does this happen? Shetlar has some thoughts.

“The current thinking of this is there are regulatory genes, just like we know that certain animals will take darker colors if their skin is exposed to colder temperatures. Now the obvious reverse of that is the arctic fox. That one, when the skin is exposed to cold weather, the hair turns white, because it wants to be white during the winter time not to stand out in the snow,” he said. “These genes regulate the expression of color in the body. The current thinking is these caterpillars are actually expressing the colors from the temperatures they were exposed to back in July and August when they were small larvae or even eggs developing as an embryo. So what they’re really telling you is what they’ve been already exposed to not what they’re going to predict coming up.”

Woolly worms are not the only insect thought to predict the weather. The amount of spider webs seen before the upcoming winter is a sign to some, taking that as an indicator of hard times ahead.

“People have heard the term gossamer thread and they might not know what that is. It has sort of lost favor as people get out of the rural and agricultural areas. But the vast majority of spiders actually are like Charlotte in Charlotte’s Web. If you remember the sort of tear-jerking part of that story, Charlotte dies at the end of the season but she lays an egg case. That’s what most spiders do. At the end of the season, the females will mate, and they’ll lay an egg case. For about half of the species of spiders, those eggs will hatch in the fall and those little spiderlings will climb up to the tops of grasses and shrubs, spin out a thread of silk, which is a gossamer thread, and they’ll actually do what we call ballooning. If there’s enough wind, that wind will pick up the little thread of silk with a little spiderling on the end of it and they’ll go for a ride to try to find new territory and get away from all their siblings that hatched out of that same egg mass,” Shetlar said. “Gossamer threads are just one of the things that occur in the fall, and in reality what it usually means is we have a warm spell with some wind in it. And I noticed this a couple of weeks ago when we had our last warm spell. It was a nice sunny day and I could look out over a field and there were just these hundreds of little shimmery threads that were glistening in the sun. Those were the gossamer threads of the little spiderlings.”

Scientific or not, it’s always a good time to find our furry caterpillar friends crawling away from the winter ahead. From what I’ve seen, we’re looking at a rough winter ahead. But isn’t it supposed to be every year?

Only time will tell.

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