Move over Puxatawney Phil, there may be a new furry meteorologist in the Chesapeake Bay watershed! That’s right, the Wooly Bear Caterpillar (larvae of Pyrrharctia isabella) has been rumored to be able to predict the harshness of the upcoming winter!

What are Woolly Bear Caterpillars?

If you have been out in the forests of the Chesapeake Bay Watershed this fall, you have most likely seen HUNDREDS of these little fluffy friends crawling around looking for a nice warm bed of leaves to hunker down in for the winter. These little guys and gals are the larvae of the Isabella Tiger Moth and have a remarkable way of surviving the cold winter months. During the fall, they roam around, trying to find a safe, sheltered spot amongst fallen leaves and logs to freeze during the winter! These caterpillars produce a substance called glycerol, which is like a natural antifreeze for their cells! As the weather gets chillier, the Wooly Bears slowly freeze and glycerol prevents their inner cells from rupturing. This sends them into a hibernation-like state, so that they can thaw out in the spring and begin building their transformative cocoon.

Woolly bear caterpillar (Photo by Herald Times Reporter).

Why do people think they can predict the winter?

The folklore that Wooly Bear Caterpillars can predict the severity of winter weather comes from a 1948 scientific study by a scientist named Dr. C.H. Curran, the curator of insects at the American Museum of Natural History in New York City. Dr. Curran decided to research the Woolly Caterpillars’ weather predicting ability after noticing the variations in their band lengths. He conducted his study in an area in the Bear Mountain State Park in New York. For eight consecutive years, Dr. Curran collected Woolly Bear samples and measured the length of their bands and compared them to the consecutive winter season. He determined that if the orange band was longer, the winter would be more harsh. This study was published in the New York Herald newspaper, which started the widespread belief that the Woolly Bears are nature’s meteorologists.

Wooly Bear Caterpillar Winter Predictions. 27 July 2025.

The answer we have all been waiting for…. Can Wooly Bears actually predict the winter?

The short answer is… no. These lovely, banded creatures cannot predict the upcoming winter. The orange band is an indicator of the caterpillars’ growth and age. If the orange band is wider, it means that the caterpillar is older and has had more time and resources to grow. Each time a Wooly Bear sheds its skin, its orange band grows a bit larger. Dr. Curran’s research is unreliable because it was confined to a small area in New York and for a short period of time, making it not conclusive scientific proof. I guess your job is safe for now Puxatawney Phil.