Woollybear is a common name for the caterpillar stage of several species of tiger moths. Woollybears have dense, stiff, hairlike coats. In North America, the most familiar of these caterpillars is the banded woollybear, the larva of the Isabella moth.
The banded woollybear is black on both ends and has a reddish-brown band around the middle. It feeds on plants and grows to about 1 1/2 inches (4 centimeters) in length. In autumn, the fully grown caterpillar finds a sheltered spot, such as under bark or leaves. It remains there inactive during winter. In spring, it spins a loose cocoon of silk and hairlike parts around itself. An adult moth emerges from the cocoon after 3 to 4 weeks.
According to folklore, the coat of the banded woollybear can help forecast the severity of the coming winter. A narrow reddish-brown band on the coat is said to indicate a milder winter than a wide band. Scientists believe that the differences in the widths of the bands are related to current temperature and moisture conditions rather than to the outlook for cold weather.
