The woolly bear is a common and well-known caterpillar. Though most people have one kind of woolly bear in mind, there are 8 or more species in the U.S. that could legitimately be called woolly bears because of the dense, bristly hair that covers their bodies. Woolly bears are the caterpillar stage of medium sized moths known as tiger moths.
The best-known woolly bear is called the banded woolly bear. It is black at both ends and reddish-brown in the middle. The adult is called the Isabella moth. The banded woolly bear is found throughout the U.S., Mexico and southern Canada but not the rest of the world. There are 2 generations of caterpillars each year (May and August) The second generation is the one noticed in late fall when the woolly bears are crossing the roads, usually in great haste as if they have someplace special to go. In fact they are only scurrying to find a sheltered location under dead plant debris, etc. where they will spend the winter as a larva. In the spring they will feed briefly before changing into a cocoon and eventually a moth. Eggs laid by the female moths start the cycle over again.
The adult moth of the banded woolly bear has white wings with scattered black spots. Wingspan is about 2 inches.
The banded woolly bear is the species mentioned in winter-prediction folklore that claims longer the black at the ends of the body, the more severe will be the coming winter. As you might expect, science has debunked this legend by showing the amount of black varies with the age of the caterpillar and the moisture levels in the area where it developed.
This doesn't stop the good folks of Vermilion, Ohio (west of Cleveland) from holding an annual "Woolly Bear Festival" -- claimed to be the largest one-day festival in Ohio. Festivities include a parade, woolly bear races and an "official" analysis of the woolly bears and forecast for the coming winter.
For more information on tiger moths, including rearing instructions, you can visit this page at the Michigan Entomological Society website.