KDSN RADIO News
Can a caterpillar really predict whether Iowa will have a mild winter?
An expert at Iowa State University’s Insect Zoo says there may actually be some science behind the folklore about how the thickness of the wooly bear caterpillar’s stripes can help predict the severity of the winter ahead.
Ginny Mitchell, the insect zoo’s education program coordinator, says a fellow entomologist in New York studied the fuzzy creatures in the 1940s.
“He sampled all of the wooly caterpillars in the area for nine years, and during that time, there was actually some correlation between the markings on the wooly caterpillar and the winter,” Mitchell says, “but that study had a very small sample size, so people do not consider it scientifically factual.”
The brown and black caterpillars are prevalent in Iowa right now as they’re looking for safe places to spend the winter ahead. As the story goes, Mitchell says the thickness of the caterpillar’s center stripe is key in weather forecasting.
“The rusty, kind of orange color, if that band is really big, that means we’re going to have a mild winter,” Mitchell says. “If the black parts of the wooly caterpillar are very large, it’s going to be a more severe winter. If there is more hair on the wooly caterpillar, then that means that it’s going to be a more severe winter.”
There are also theories that if the caterpillar is crawling south when you find it, it’s trying to flee the northern cold, and the reverse if it’s heading north, a mild winter is ahead.
At least two communities — Vermilion, Ohio, and Banner Elk, North Carolina — have fall festivals devoted to the alleged prognosticating abilities of the wooly bear caterpillar. One remarkable fact, Mitchell says these fuzzy critters hibernate during the winter and their bodies contain a sort of natural antifreeze.
“Say you’re out raking leaves or moving some brush and you find one, it will kind of look like it’s dead. It’ll be curled up like a ‘C’ and it won’t be moving very much,” Mitchell says, “but if you take it inside and you warm it up, then it’ll start to move.”
There are reports of wooly bear caterpillars surviving temperatures as low as 90-degrees below zero, even spending an entire winter frozen in an ice cube to emerge just fine in the spring. Once temperatures warm, it will create a cocoon and emerge a few weeks later as an Alexandra or Isabella tiger moth.