In the width of a caterpillar band

Posted By DAVID HAWKE

Posted 2 months ago

This lovely open fall has certainly provided ample opportunity to get outside and do at least some of those autumn chores. We still don't have the storm windows hauled out yet, but are much better prepared for winter than we were for last year's early start with the white stuff.

While doing some tidy-up work around the yard, I found several woolly bear caterpillars, a cute reminder of childhood folklore. You know the old story: the width of their band predicts the severity of the coming winter. These fuzzy-looking moth larva, with their brown and black coloration, are a definite sign of late autumn as they seek out a place to hibernate.

These caterpillars belong to a unique group of animals that produce their own antifreeze. A bit of protection from the cold is all they need, such as behind some loose bark or under a pile of old lumber. Despite the minus twenty-something temperatures we'll have, these caterpillars will survive and wake up next spring, then turn into a cocoon.

Late in the spring, an adult Isabella tiger moth will emerge, mate, lay eggs and die. The eggs hatch, the caterpillars eat low-lying vegetation and grow until next fall. The true story of predicting winter comes from these two sentences.

Each full-grown caterpillar has 13 body segments. Each segment is covered with bristles, and each segment of bristles has a colour. So the first mistake is now cleared up, in that they are not covered in wool, only sheep and muskoxen have that stuff on their bodies. These thick bristles are the caterpillars defence against raccoons, skunks and desperately hungry robins.

The width of the central brown band is determined by whether or not the two end bands, which are black, are confining the brown or not. The folktale says that a wide brown band indicates a mild winter, while a narrow brown band is a sign of a wickedly miserable winter (and I ask you, is there any other kind of winter?).

Apparently, this method of seasonal prognostication stretches back for generations (of people, and Isabella tiger moths). This nugget of natural wisdom rides alongside such tales as groundhogs seeing their shadows, squirrels gathering huge quantities of nuts, and the size of the liver in an autumn slaughtered hog. Who needs Environment Canada when all these omens are readily available?

Since it's not always possible to attend a hog slaughtering, scientists have looked into the reliability of woolly bear coloration. And surprise, there is a bit of truth to the fur coats of these caterpillars. But not what you'd expect.

First off, a Dr. C. H. Curran, of the American Museum of Natural History, New York, and wife, began studying these invertebrates in detail starting in 1948.

When the fall colours were at their peak, Dr. C. H. Curran, and wife, would go to Bear Mountain, catch woolly bears and measure their band widths. (Bet I know who did the camp cooking while what's his name was flipping logs looking for sleepy caterpillars.)

For eight years, Curran, and wife, studied these caterpillars and found little relationship between band width and weather. Of the 13 body segments, usually only five had brown bristles, although that number did change a bit.

However, a local newspaper ran a story on their, I mean his, studies and suddenly there was "proof" of the folktale. In keeping with the "tongue-in-cheek" attitude of the event, Dr. Curran and wife formed the Original Society of the Friends of The Woolly Bear, meeting each fall to find and measure said creatures.

Further research has yielded some other interesting facts of this bandwidth discussion. Apparently, caterpillars that live in wet areas have narrow brown bands, and wide-banded caterpillars come from dry habitats. No explanation has been given for this phenomenon, but research numbers don't lie (although they may get misinterpreted from time to time).

The most plausible explanation of the ever-increasing brown band comes from some independent study (not sure if wives were involved) that linked the age of the caterpillar to the width of the band. The older the caterpillar, the more brown bristles there are. This is a result of the molts, or instars, a caterpillar goes through as it ages.

So, if you have a mild spring and the hibernating caterpillars wake up early, they form cocoons early and hatch early and lay eggs early and the caterpillars are weeks older by the time they are discovered by scientists and little kids in the fall. If the spring is harsh and hangs on, the caterpillars wake up late and are still young and growing when fall arrives.

Do you see where this is going? The width of the brown band tells us what last winter was like. Duh! Nature is so confusing. I think it's time to start raising a few hogs.