Do Woolly Moths Hibernate Inside a House?

The banded woolly bear caterpillar, also called the woolly worm, is the larval form of the Isabella tiger moth. Most moths overwinter as pupae, but the banded woolly bear is unique because it spends the winter as a caterpillar. In the fall, these furry black and orange caterpillars can be seen racing to find warm spots to wait out the winter. They aren't common house dwellers, but the occasional caterpillar might wander into your garage.

The banded woolly bear caterpillar is easily recognizable. Its entire body is covered in hair so it looks a little like a fat, fuzzy pipe cleaner. It is banded on each end with black with a rusty orange center. The width of the three bands can vary. The adult of the banded woolly bear is the Isabella tiger moth. The upper-side of the forewing is dull orange to yellow-orange with a few diffuse black spots. The upper-side of the hindwing is pale to bright pinkish-orange also with diffuse black spots.

These furry caterpillars spend the winter as caterpillars as opposed to pupae like most moth larvae. According to the University of Illinois Extension, the hairs covering the caterpillar's body might serve as insulation against the cold winter weather. As winter approaches, these black and orange beauties begin to leave their solitary feeding grounds in search of a sheltered spot to spend the winter. Houses aren't typically a place a woolly bear would overwinter. They prefer the outdoors and can be found under debris or rocks, in leaf litter or in any other spot sheltered from harsh weather. The occasional stray might find its way into a house or garage, but this is not typical behavior.

After their winter dormancy, banded woolly bears emerge in the early spring. They will feed and then pupate, emerging as adults in late spring. Adults mate and lay eggs in early summer. The summer generation of banded woolly bears is less conspicuous as they spend their lives in hiding. This generation lays eggs that will hatch in late summer, giving rise to the overwintering generation.

As solitary feeders that prefer sheltered, out-of-the-way feeding spots, banded woolly bears are rarely seen in the summer. In the fall you can observe them crossing roads or sidewalks in search of safe overwintering sites. Caterpillars feed on a wide range of plants, including sunflowers, asters, birch, clover and corn. Ranging throughout the United States, woolly bears are common, but not considered a pest.