NOVEMBER
2013

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

Download the audio files or subscribe to our podcast.

 

Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

11-14-13

Download the audio of On Six Legs: MP3, WMV
Follow us online at Purdue Agriculture News Columns

Woolly-Worm, Winter-Weather Witchery


wooly worm
Banded woollybear caterpillar

Photos by John Obermeyer/Purdue Entomology

You can count on it. It happens every year in October and early November. I'm not talking about the days getting shorter and the air getting colder. I'm talking about someone asking what the woolly worms are saying about the upcoming winter.

It seems that woolly worms rank right up there with squirrels hoarding nuts, husk length on ears of corn and thickness of fur on rabbits as prognosticators of winter severity.

But not any old woolly worm will do when it comes to making winter predictions. One particular species of woolly worm has gained a certain amount of fame in this area. There are even annual fall festivals devoted to this particular woolly worm. Two of the oldest are in Vermillion, Ohio, and Banner Elk, N.C.

The woolly worm featured in these festivals has the "official" common name of banded woollybear. The name is official because it is the one listed in the Entomological Society of America's Common Names of Insects & Related Organisms publication. But there are other common names also used for this caterpillar, including black-ended bear and fuzzy wuzzy. This fuzzy caterpillar is called banded because it is black on both ends with a reddish brown band in the middle.

The banded woollybear has the habit of curling up and remaining motionless when disturbed. According to J. H. Holland, author of The Moth Book, such behavior is related to the U.S. slang phrase, "to caterpillar." Holland states that "to caterpillar" means "to silently succumb and yield to the unavoidable." That sounds very much like "playing possum" to me. Anyone who has ever picked up this woollybear caterpillar has probably witnessed such behavior!

Tiger moth
Tiger moths isabella

The woollybear caterpillars become moths after they pupate. The banded woollybear is scientifically classified as Pyrrharctia isabella. Known as the isabella moth, it is one of the so-called tiger moths. These are medium-sized moths with a wingspan of about two inches; they are usually conspicuously spotted or banded. The caterpillars of tiger moths are normally hairy, which is why they are known as woollybears or woolly worms.

J. E. Smith named this moth in 1797 with the species epithet of isabella. The name isabella probably has nothing to do with Queen Isabella of Spain, who many history buffs know was instrumental in bankrolling Christopher Columbus' first voyage to the New World. Isabella likely was chosen as the species name because the word means a buff-brown color, which is descriptive of the moth.

So why has this particular species of woolly worm earned a venerated spot among animals that predict winter conditions? No one knows for sure, but at least three factors have probably contributed to this woolly worm becoming a winter-weather prophet.

The first reason is that the caterpillar has very distinctive markings. That means most people recognize the caterpillar when they see one.

Another reason is the behavior of these woolly worms. They are often seen scurrying across sidewalks and roadways on warm and sunny days during fall. This species of moth spends the winter hibernating as a caterpillar. The caterpillars seek protected sites for their winter snooze. However, the caterpillars never seem to be satisfied with any site and keep crawling around when temperatures remain warm.
 
A third reason is that the isabella moth is a common insect. That is partially because the caterpillars feed on a wide variety of food plants found in many different habitats. Food plants range from hardwood trees to plantain - a common roadside plant and lawn weed.

So how accurate is the brown-banded caterpillar of the isabella moth in predicting the winter weather? Spoiler alert: not at all! It is folklore, pure and simple. There are several versions of how to read the woolly worms, including direction of travel, density of coat and width of the brown band.

So here's your handy-dandy, woolly-worm, winter-weather guide. Worms crawling south, expect a cold winter; crawling north, expect a mild winter. Unusually fuzzy worms mean a cold winter; less fuzzy, a mild winter. A narrow brown band indicates a cold winter, while a wide brown band means a mild winter is on the way.

I saw a really fuzzy black woolly worm crawling south in my barn today. I can't decide if I should buy more winter fuel or just head to Florida for the winter!

 

 

 

Writer: Tom Turpin
Editor: Olivia Maddox