Tag Archives: Wooly Bear caterpillar life cycle

Wooly Bear Caterpillar

I am often asked about the Banded Wooly Bear caterpillar and questions range from, “Why am I seeing a Monarch caterpillar in the fall” (the Wooly Bear is not a Monarch caterpillar) to “how will the Wooly Bear survive the winter?”

The Wooly Bear caterpillar is the larva stage of the Isabella Tiger Moth. They are typically seen in autumn as they search for a place to curl up for the winter–under a rock, log or leaf debris or in the chinks of bark. The heavy coats of members of the Acrtiid family of moths help them overwinter, along with their ability to produce a natural sort of antifreeze called cryoprotectant.

Banded Wooly Bear Caterpillar (Pyrrharctia isabella)

The following spring, the caterpillars emerge from their winter nap, begin to feed, form a cocoon (pupate) and emerge as the adult form of the Isabella Tiger Moth. Female Isabella Tiger Moths deposit their eggs on a wide variety of plants including birch, elm, maples, asters, sunflowers, spinach, cabbage, grass, and plantain; all caterpillar food plants. In our region there are usually several generations per year and it is the last generation of the growing season that over winters, nestled in, well-hidden and wrapped in their furry coats.

Fun fact from wiki: Caterpillars normally become moths within months of hatching in most temperate climates, but in the Arctic the summer period for vegetative growth and hence feeding is so short that the Woolly Bear feeds for several summers, freezing again each winter before finally pupating. Some are known to live through as many as 14 winters. 

Isabella Tiger Moth (Pyrrharctia isabella)

Isabella Tiger Moth image Courtesy wiki