Insect Signs of Fall: Part I

Signs of fall are all around us:  brilliantly colored leaves of crimson and gold; honking geese flying overhead in “V’s”; and sunsets that fall ever earlier.  But some signs of fall are a bit more subtle.  Insects are getting ready for winter, and their changes in behavior foreshadow the coming winter.  

A Wooly Bear found at NBNC in early October, 2010

In Part I of our “Insect Signs of Fall” series, we look at a very familiar insect: the Wooly Bear.  Wooly Bears are neither bears, nor can we shear them for wool.  They are the caterpillars of the Isabella Tiger Moth (Pyrrharctia isabella).  The adult moths are aloft during the summer months.  They are drab in color and not a moth that would naturally catch your eye.  The caterpillars, however, are fuzzy with black hairs at both ends, and a brown, hairy center.  

adult Isabella Tiger Moth
photo by Tom Murray
courtesy of bugugide

Wooly Bears feed on a variety of vegetation, including grasses, asters, clovers, birches, maples, and others.  This time of year, they are frequently seen wandering in lawns, roadways, and sidewalks as they search for a location to spend the winter.  In the spring, they will form a cocoon and transform into an adult moth.

The length of their brown stripe can vary by individual, and folklore suggests that the length of the brown band can be an indicator of how harsh the upcoming winter will be.  The Wooly Bear below is an good example of how variable their appearance can be.  This myth has no factual foundation, so don’t count on these caterpillars to tell you the seasonal forecast.

Text and photos by Larry Clarfeld, unless otherwise noted.