Your Land & Water October 2026

2 days ago

4 min read

Updated: 24 hours ago

Woolly Bears!

If you’ve ever seen a fuzzy black-and-reddish-brown little critter inching its way across your patio, paths or driveway at this time of year, then you’ve encountered a Woolly Bear Caterpillar, also known as a Banded Woolly Worm. The species actually appears abundant in South Jersey right now, because these visually striking caterpillars are out and about actively seeking sanctuaries in which to overwinter. If you touch one (which will not hurt you, but could possibly irritate your skin), they respond by curling into a defensive ball to mimic playing dead.

Woolly Bear Caterpillar courtesy of University of Missouri

This caterpillar is the larva of the Isabella Tiger Moth (Pyrrharctia isabella), an attractive, medium-sized moth with yellowish to orangish forewings with a few sparse spots on its wings, a black spot on each of its 13 segments, bright reddish-orange legs, and a wingspan of about 4.5 – 6.5 cm (1.75 – 2.5 in). It is found in meadows, fields, gardens, woodland edges, and roadsides across the United States, Canada, and into northern Mexico.

Isabella Tiger Moth Photo by Andy Reago & Chrissy McClarren/Wikimedia Commons — Isabella Tiger Moth *Photo by Andy Reago & Chrissy McClarren/Wikimedia Commons*

The Woolly Bear Caterpillars you see will hibernate for the winter under bark, leaf litter, or logs. They survive freezing temperatures by producing a cryoprotectant, essentially an antifreeze, allowing most of their body mass to freeze solid although the freezing occurs outside their cells rather than within them.

The caterpillar emerges from its egg in the fall, feeds on a wide variety of plants including dandelion, aster, plantain, clover, grasses, birch, maple, elm, sunflower, and more. As temperatures cool, it finds shelter where, first, its heart stops beating, then its gut freezes, then its blood, followed by the rest of the body. In the spring, beginning in late March it will thaw safely, spin cocoons, and emerge as an adult moth in April. Larval lifespan varies from a few months to nearly a year, with the Isabella Tiger Moth producing one or two generations per year, during June, July, and September, depending on location. Moths living farther north have a longer time in their larval stage.

Woolly Bear curled up in a ball https://:stock.adobe.com

Folklore in the U.S. and Canada has long considered the Woolly Bear as a predictor of the forthcoming winter’s severity. The ratio of black to reddish-brown on the body is the determinant, measured by counting the body segments under each color. The wider the rusty brown sections of a Woolly Bear Caterpillar (or the browner or darker the middle section is), the milder the coming winter will be. The wider the black sections are, the harsher the winter.

Another version of this belief is that the direction in which a Pyrrharctia isabella crawls predicts the winter weather, with the caterpillar crawling south to escape colder weather. So far, there is no evidence that either superstition is true. Hatchlings from the same clutch of eggs can display considerable variation in their color banding, and a larva's brown band tends to widen with age as it molts. Several scientific studies have been done about Woolly Bear Caterpillar forecasts, including one by the American Museum of Natural History. None of these studies have shown any correlation between Woolly Bear markings and the severity of the upcoming winter.

*Photo by SillyPuttyEnemies/Wikimedia Commons*

However, according to Almanac.com, Mike Peters, who spent more than 30 years teaching entomology at the University of Massachusetts, once said there could, in fact, be a link between winter severity and the brown band of a Woolly Bear Caterpillar. “There’s evidence,” Peters said during his UMass tenure, “that the number of brown hairs has to do with the age of the caterpillar—in other words, how late it got going in the spring. The [band] does say something about a heavy winter or an early spring. The only thing is … it’s telling you about the previous year."

Still, there are Woolly Bear festivals in several places in the fall, according to Wikipedia:

Vermilion, Ohio, in October, begun in 1973, the Woollybear Festival features woolly bear costume contests for children and pets and the Woolly bear 500 caterpillar races.
Banner Elk, North Carolina, has the Woolly worm festival begun in 1977, that features crafts, food, and races. The winning woolly bear predicts the winter weather for the following winter.
Beattyville, Kentucky, begun 1988, called the Woolly Worm Festival, features food, vendors, live music, and a Woolly Worm Race in which people race the woolly bear caterpillar up vertical strings.

So, you can enjoy this charming lore, and you can look at any local Woolly Bears you find to determine how well they forecast this coming winter. But you are probably wiser to rely on advanced weather prediction services, especially since this winter prediction method is only number 18 out of 20 in the Old Farmer’s Almanac!!