The Parklands

Where Are You Going Wooly Bear?

By now the wooly bear caterpillar (Pyrrharctia isabella) has become a familiar site in The Parklands.  You may have seen them crossing park roads or the Louisville Loop trail.  They are easily recognized by their fuzzy black bodies with a brown band across their backs. Children are amazed by the fuzzy little creatures that curl up into a tight round ball when touched.They were plentiful in The Parklands throughout October and can still be seen on sunny fall days. They seem to be in a hurry to get somewhere, but where are they going?

In the coolness of fall the wooly bear caterpillars begin their search for a proper place to spend the winter months, burrowing under leaf litter and logs.  As the temperature drops so does the body temperature of the wooly bear, metabolism slows and they enter a period of hibernation similar to the mammalian bears. Wooly bear caterpillars produce a cryoprotectant in their circulatory fluids which prevents damage to their body tissues and allows them to actually freeze solid in the winter. Folklore has it that the size of the brown band on the caterpillar can predict the severity of the coming winter. While most scientists rule out this connection, the life cycle of the wooly bear may provide some interesting clues about the climate of an area.

As the caterpillars grow, they molt and go through several instars before they are full-grown and can complete metamorphosis to become Isabella Tiger Moths. The color of their bristles changes as the caterpillar undergoes each molting, with each molting the black bristles are replaced by bristles with a brown or orange color. Their spring and summer growth is dependent on the length of the season.  In very cold climates, such as northern Canada, the wooly bear may hibernate up to 13 times before completing metamorphosis.  Here in the temperate climate of Kentucky the wooly bear can complete two generations in one year. In the spring as the temperatures warm, the caterpillars wake from their winters sleep and form a cocoon to pupate, from this they emerge as Isabella Tiger Moths. The moths only live a few days during which time they mate and lay eggs.  So while we can’t necessarily predict the severity of the coming winter with these fuzzy insects, we can predict that as these caterpillars head off to hibernate, winter is surely on its way.  We can expect to see abundant Isabella Tiger Moths in spring!

Want to keep a pet Wooly Bear Caterpillar over the winter and see if it is ready to become a moth in the spring?  Check out the following link for everything you need to know:

Don’t forget to release the moth in the spring so it can complete its life cycle! 


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