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Can Woolly Bear caterpillars predict the coming winter?

My nephew IS THE CUTEST (Yes, I am biased, no that doesn't change the facts)! My sister sent me a video of him discovering a Woolly Bear caterpillar on an apple tree. The caterpillar was hustling through the lower tree branches and my nephew ran around the tree, always in search of the perfect view. My sister and I LOVED finding these caterpillars when we were younger (ok, we still throughly enjoy finding them as adults), as I think do most kids.


According to folklore, the amount of black on the woolly bear in autumn varies proportionately with the severity of the coming winter in the location where the caterpillar is found. Supposedly, the longer the woolly bear's black bands, the longer, colder, snowier, and more severe the winter will be. Similarly, the wider the middle orange/brown band you can count on 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 other versions to this story. One version 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 bear's crawling in a southerly direction are trying to escape the cold winter conditions of the north. On the other hand, woolly bear's crawling on a northward path would indicate a mild winter... but seriously on this last one... is the couple miles a caterpillar can travel really going to make a difference... I doubt it.


The popularity of the woolly bear caterpillar has resulted in several festivals honoring them. Since 1973, the residents of Vermilion, Ohio have held an annual "Woolly Bear Festival". The festival is the brainchild of legendary Cleveland TV personality Dick Goddard, longtime weatherman at WJW-TV. It is claimed to be the largest one-day festival in Ohio. Festivities include a parade, woolly bear races and an "official" analysis of the woolly bears and forecast for the coming winter.  Also, every 3rd weekend in October the annual Woolly Worm Festival is held in Banner Elk, NC.  They begin their worm races around 10:20 AM, or as soon as the first heat, on Saturday morning. Races continue all day until the grand final about 4 PM when the champion worm and trainer is crowned (and paid!). At that time, the official winter forecast will be declared. Sunday worm races are for fun and small prizes and will continue throughout the day as long as there are race participants. Other festivals are held in Beattyville, KY (began in 1987); Lewisburg, PA (began in 1997); Oil City; PA (began in 2008); and Lion's Head, Ontario (began in 2011).


Even though it is widely believed that the woolly bear caterpillar can predict the upcoming winter's severity, the truth is the woolly bear caterpillar's coloring is based on how long caterpillar has been feeding, its age, and species. The better the growing season is, the bigger it will grow. This results in narrower red-orange bands in its middle. Thus, the width of the banding is an indicator of the current or past season's growth rather than an indicator of the severity of the upcoming winter... but it would be interesting to check the growing season in comparison to the severity of winter over the years... just to see.  


Also, the coloring indicates the age of the woolly bear caterpillar. The caterpillars shed their skins or molt six times before reaching adult size. With each successive molt, their colors change, becoming less black and more reddish. In addition, there are approximately 260 species of tiger moths (the adult of the woolly bear caterpillar) in North America, and each species has slightly different color patterns and hair coverings. As a result, some of the color and hair variations that we see each fall are a result of these different species.


As far as the story about the woolly caterpillar's coat, this is how Mother Nature helps it survive winter. The fur is called setae and it isn't there to protect them from the cold weather. Instead it actually helps them to freeze more controllably. Here is something truly remarkable. Once settled in, the caterpillars hibernate, creating a natural organic antifreeze called glycerol. They freeze bit by bit, until everything but the interior of their cells are frozen. These interior cells are protected by the hemolymph. Woolly bears can - and do - survive to temperatures as low as -90ºF. This ability to adapt to cold shows up particularly in the Arctic, where the woolly worms live in a strange state of slow motion. Most caterpillars live for two to four weeks before becoming moths. The Arctic woolly worms, however, spend at least 14 YEARS in the process! The woolly bear caterpillar has even been known to survive an entire winter completely frozen in an ice cube.


As far as the woolly bear caterpillar's travel goes, they are simply moving about in search for that perfect spot to curl up and spend the winter. This is usually under bark, a rock, or a fallen log. 


The Woolly Bear winter predictor myth has been around since colonial times. However, it grew in popularity after Dr. Howard Curran (curator of entomology from the American Museum of Natural History) did a small study in 1948. He went out to Bear Mountain, New York with a reporter, his colleagues, and their wives. He counted the brown bands on 15 different specimens.  He then made a prediction for the winter. This news story was published in the New York Herald Tribune (1924-1966). It was picked up by the national press and the rest is history.




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