What Does the Woolly Bear Predict.... (11-15-12)
Today we received a call in the weather office from someone who had seen a number of woolly bear caterpillars and wanted to know what they meant for our upcoming winter. It is has been a while since I had anyone ask me about this folklore so the call sent me to the internet to do some research. The Banded Woolly Bear is the larvae stage of the moth that is known as Pyrrharctia isabella. Here in the eastern United States and Canada the appearance of a Woolly Bear caterpillar and its stripes supposedly forecasts the upcoming winter.
I pulled some of the basic information about the genesis of this weather folklore from the Old Farmer’s Almanac. It goes back to 1948 and Dr. C.H. Curran the curator of insects at the American Museum of Natural History in New York City. Over the course of nine autumns, he travelled north of the city into the Catskills and collected a number of the caterpillars. Each of the caterpillars has 13 distinct segments and Dr. Curran measured the number of segments that were orange/brown. He found that during those years when he found more caterpillars with thicker orange/brown bands, the harsher the following winters. Dr. Curran was the first to say, however, that the sample size he used was much too small to be considered a legitimate scientific experiment. Still, more than 60 years later, the theory that the Banded Woolly Bear can ‘predict’ the upcoming winter persists. Here is the full Old Farmer’s Almanac article.There are some in the insect world that think the caterpillar and its stripes are more a sign of what happened the previous winter and not what will happen. Mike Peters from the University of Massachusetts says the length of the orange/brown stripe is actually a function of the age of the caterpillar. The older the caterpillar, the wider the orange/brown stripe. That means after a mild winter like last year, the caterpillars come out earlier in the Spring and are older come Fall, thus the orange/brown stripes would be wider.So there is no scientific evidence that the Woolly Bear can forecast the upcoming winter. We have our own tools to forecast our winter and we’ll take our crack at the winter outlook early next week (either Tuesday or Wednesday)
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