This week’s crawly is wooly, but it is not a bear and it cannot predict the weather. Meet the wooly bear caterpillar (Pyrrharctia Isabella). Before we learn about the moth the wooly bear morphs into, let’s talk about the weather.
The popular folklore around wooly bears is that the size of their color bands predicts what the coming winter weather will be. According to the lore, the blacker the caterpillar is (smaller rusty band) the more severe winter will be.
Moreover, which black band is longer purportedly 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.
This folklore is so ingrained that there are even festivals celebrating wooly bears and their colorful predictions in several North American cities.
What really got the wooly bear winter prediction myth going was a fun day out in the fall of 1948. Dr. C. H. Curran, curator of insects at the American Museum of Natural History in New York City, took his wife 40 miles north of the city to Bear Mountain State Park to look at wooly bear caterpillars.
For fun, they collected several and Curran counted the colored bands then forecast the coming winter weather through a reporter friend at The New York Herald Tribune. The prediction worked out (that year) and the myth took off.
Wooly bears became caterpillar celebrities, as recognizable as monarch caterpillars. Though few folks knew what moth they’d morph into.
So, what’s the truth behind the color variations in wooly bears? Because they do vary. Pictured are three wooly bears from September 2022 and they’re a great representation of “most” wooly bears. Usually, the bands are nearly equal in size and break the caterpillar into thirds as it were.
In fact, the wooly bear caterpillar’s coloring is based on how long and how well the caterpillar has been feeding and their age. The more plentiful their food is, the bigger they will grow. This results in narrower red-orange bands in its middle. Thus, “bandwidth” really tells us how severe the past winter was. The milder the winter, the earlier they hatch and the bigger they grow.
Wooly bear bands have 20/20 hindsight!
Fun fact: Wooly bears are also called “wooly worms” (though they are not worms any more than they are bears), “fuzzy bears” and “hedgehog caterpillars” because they curl into a ball and play dead when disturbed.
You’ll see wooly bears walking around a lot in the fall, especially early in the morning (or at night if you’re out and about). They are searching for food and for a place to hibernate.
Fun fact: There’s a secondary myth that if a wooly bear is traveling south, winter will be cold, and they’re headed to warmer climes; the opposite if traveling north. Really, they’re just looking for a nice bit of bark to curl up under.
Yep, unlike most caterpillars who morph into cocoon form before winter, wooly bears hibernate until spring, then morph into cocoons and emerge as adult Isabella tiger moths in late May or early June.
I don’t have a photo of an adult, but look them up on your own; they are beautiful moths and you can look for live ones next spring.