Wooly bear caterpillars (Pyrrharctia isabella) are an immature stage of the Isabella Tiger Moth. Superstition has it that the width of the colored bands can predict the severity of the coming winter (more black = colder winter). Not surprisingly, there is no scientific evidence to support this.
There is, however, interesting science on how these caterpillars survive the winter. Unlike the Monarchs that migrate to avoid Michigan's cold weather, or other species that overwinter as eggs, pupae, or adults, the wooly bear hibernates as a caterpillar, producing an internal antifreeze that keeps it from freezing solid.
I've seen a lot of these guys in Kalamazoo over the last few days.
I teach economics at Kalamazoo College. My wife is also an economist. We were on sabbatical in Europe for the 2014-15 academic year. (Salamanca, Spain, followed by Oxford, UK.) We were in Uruguay for the 2006-7 academic year.