'Wisdom' of Woolly Bear Weathermen is Called into Question

For baby boomers, the name of the Woolly Bear Caterpillar will at least ring a bell. Much like the iconic groundhog, this incredibly fluffy black and brown caterpillar has long been associated with winter, able to help locals predict the severity of the season. However, whether or not there is any truth in the folklore has long remained a subject of debate.

The story goes like this: Every winter, countless woolly bear caterpillars hunker down, aiming to hibernate through the cold of winter just as their namesake famously does in caves and alcoves. And for some strange inexplicable reason, the length of their brown stripe just before this long sleep reflects just how nasty the approaching winter is going to be. A shorter stripe (and more black "fur") betrays that a cold and stormy winter is ahead. Likewise, the more brown you see, the milder your winter will be.

According to the Old Farmer's Almanac, Dr. Howard C. Curran, a curator of insects at the American Museum of Natural History in New York City, decided to see if there was any truth to this legend back in 1948. He and his wife reportedly traveled up to Bear Mountain State Park and spent a day observing and collecting woolly bear caterpillars.

The bugs at this time were near-frozen, making collecting them under logs or leaf-cover relatively simple. But they weren't dead. Entomologists today know that these insects boast a similar natural antifreeze found in some fish and rare amphibians, where they can freeze stiff without suffering from cell damage.

Afterwards, Curran counted the average length of reddish brown coloring amongst his samples (as determined by segment count), and then attempted to forecast the approaching winter weather. These forecasts became widely popular after being reported through one of Curran's friends at The New York Herald Tribune, and went on for several years.

According to the curator, he was trying to scientifically find a weather rule-of-thumb that reflected the truth in this unusual legend. And amazingly, most of Curran's predictions about mild winters did indeed prove true.

"But Curran was under no scientific illusion," the Almanac added. "He knew that his data samples were small. Although the experiments popularized and, to some people, legitimized folklore, they were simply an excuse for having fun."

And just good ol' fun may be all to this intriguing legend. That's at least according to J. Peter Coppinger, a professor of Biology at the Rose-Hulman Institute of Technology, who says that while the woolly bear caterpillar is a remarkably hearty and intriguing insect, it actually makes for a terrible weatherman. (Scroll to read on...)

The expert recently wrote on the subject in The Conversation, saying that "there is little reliable or repeatable evidence linking the severity of winter with the breadth of the woolly's stripe."

However, when invesitgators sought to detemine what led to the variability in brown stripe length from year-to-year, they found out they can actually tell us about the weather.

"Unfortunately," Coppinger added, "it was the weather last spring."

Each year, when spring rolls around and the ground thaws, the woolly bears miraculously wake from their chilled slumber to start building a chrysalis and begin pupation. Weeks later, the incredibly fuzzy caterpillar emerges as a beautiful, and equally fuzzy moth.

In a week's time, these nocturnal moths mate, lay eggs, and die, and soon new woolly bear caterpillars are born.

According to Coppinger, as a woolly bear ages, its center segments grow longer and larger, resulting in more brown hairs on its body. In that sense, the oldest and fattest of these worms will almost always be the brownest, born during a warm spring with an early thaw.

Still, the expert acknowledges that this explanation is not nearly as mysterious nor exciting as a good legend.

"It's hard to let go of beloved folklore" he added. "Personally, I love cold, harsh, snowy winters. While I no longer believe that caterpillars can predict the weather, I still can't help smile when I find an all-black woolly bear caterpillar."

Coppinger goes on to banish illusions about a few other folk wisdoms, and if you can handle the truth, you can read about them at The Conversation.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).