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Woolly Bears on the Move

Although it’s fun to try to predict the severity of the coming winter by the amount of brown on a woolly bear caterpillar (the more brown = the milder the coming winter, according to folklore), the coloration of any given woolly bear caterpillar has more to do with its diet and age than the coming weather.  The more a Woolly Bear eats, the more frequently it molts, and each time it molts a portion of the black hairs (setae) is replaced by brown ones.  A Woolly Bear can molt up to six times — the best fed and oldest woolly bears, which have molted the most number of times, have the widest brown bands. (After overwintering as caterpillars, Woolly Bears pupate and emerge as small, brown moths called Isabella Tiger Moths, Pyrrharctia isabella.)

2 responses

  1. Llyn Ellison

    On a recent Appalachian Trail backpacking trip in TN/NC I came across what looked like a woolly bear caterpillar except it was all white. Would this be part of the same family?

    October 17, 2012 at 11:44 pm

    • Hi Llyn,
      Chances are that your “hairy” white caterpillar was in the Arctiidae family, along with tiger moths (including the woolly bear/Isabella tiger moth)), lichen moths and wasp moths. There are several species that are mostly white, including the hickory tussock moth, the scarlet-bodied wasp moth and the virginia ctenucha in the northeast. There may well be even more white species in this family in the south.

      October 18, 2012 at 12:02 am

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