The hairy caterpillar of any of various moths, especially that of the North American tiger moth Isia isabella, having a reddish-brown middle stripe and black at either end. or wooly bear Caterpillar of a tiger moth. The larva of the Isabella tiger moth (Isia isabella), known as the banded woolly bear, is brown in the middle and black at both ends. The width of the black bands is purported to predict the severity of the coming winter: the narrower the bands, the milder the weather will be