The All-Black Woolly Worm

Bill's Blog

All black woolly worm

Well look at this! While on a walk through the woods at Yankee Springs yesterday (Wed.), I came across this caterpillar. It looks to me like a woolly worm. For decades the woolly worm has been given the legend of being able to forecast the severity of the coming winter.

In the fall of 1948, Dr. C. H. Curran, curator of insects at the American Museum of Natural History in New York City, took a trip to Bear Mountain State Park to look at the woolly bear caterpillars.

Dr. Curran collected as many caterpillars as he could in a day, determined the number and size reddish-brown segments, and forecast the coming winter weather through a reporter friend at The New York Herald Tribune.Dr. Curran’s experiment, which he continued over the next eight years, attempted to prove scientifically a weather rule of thumb that was as old as the hills around Bear Mountain.

Over the next 8 years, Dr. Curran continued to look at the woolly bears and noted a faint correlation between the thickness of the brown segments and the severity of the winter than followed. The bigger the brown width, the milder was the winter.

My first thought was “correlation without causation” – like “98% of all billionaires drank milk as a kid, therefore to be a billionaire, drink milk”. There is a correlation, but drinking milk has nothing to do with becoming a billionaire.

Anyhow, the legend took off…there are woolly bear festivals and occasional news stories about the critters. Now back to the question at hand. If there is NO black band – does that mean this will be an unbelievably cold an snowy winter? Well, no. The Old Farmer’s Almanac says: “If you find an all-black woolly caterpillar, don’t worry—this doesn’t mean that we’re in for a severe, endless winter! It’s just a caterpillar of a different species, and is not used for forecasting. The same is true for all-white woolly caterpillars.”

Whew! Just to be sure…I signed my season snowplow contract to get my driveway done. I actually liked shoveling snow…but at the winters of 2014 and 2015, my back told me you don’t want to do this anymore.

We’ll have the winter forecast out around the end of October. Looks like La Nina this winter.

Isabella moth

BTW – the woolly bear caterpillar turns into the Isabella moth.

Copyright 2020 Nexstar Broadcasting, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.

Weather Tools