What about the wive's tale which claims the amount of orange/red on the Woolly Bear indicates how harsh the winter will be? It's just that—a wive's tale. Even within a single batch of eggs, each caterpillar can vary in the ratio of black to orange. The central band also grows with age, and it has nothing to do with the weather.
|An adult Woolly Bear, known as an Isabella Tiger Moth.|
The species covered in this post are only a fraction of the fuzzy caterpillars out there—there are dozens and dozens of other species. If you're really interested in identifying caterpillars of all kinds, I highly recommend the Princeton Field Guide to Caterpillars of North America. It is a wonderful guide to caterpillars if you live in the Eastern US!