Thursday, December 31, 2015

Woolly Bear

Insects in Winter

Woolly Bear
Seeing an insect slowly crawling across the trail in front of me last week was a surprise.  I knew Wooly Bears were common but had never noticed one alive and active so late in the season.  Our good weather in December must have contributed to its late activity.

The Woolly Bear is the larval form of the Isabella Tiger Moth (Pyrrharctia isabella).  Its adult form is a smallish moth with light orange wings and orange body with black dots running down the length.  It is found in many cold regions including the Arctic.  

In some areas it is called the Woolly Worm.  In the USA there are Woolly Bear Festivals!  The Woolly Bear is not 'woolly' at all.  It is actually covered with stiff bristles and feels much like a stiff brush.  

Folklore tells us that the Woolly Bear is a weather predictor.  As the story goes, the width of the black bands on the front and rear of the caterpillar are indicative of the coming winter weather.  If the bands are narrow, we will have an easy winter.  Conversely, if the black bands are broad, we will have a severe winter. 

Isabella Tiger Moth  [Internet Photo]
The Woolly Bear (Isabella Tiger Moth) completes its life cycle in one year in the temperate zones of North America.  Farther north it may take more than one year.  In the Arctic it may take several years because of the short season for the caterpillars to feed.  Some have been known to take up to 14 years!  How does it do this?  Well, the Woolly Bear caterpillar can freeze and thaw without damage.  

The adult moths lay their eggs in summer and the larvae develop over the summer to become the Woolly Bear caterpillar, as we know it, by late summer.  In late fall they disperse, looking for suitable sites to overwinter, in holes in rocks and trees and logs.  There they freeze solid.  In spring they thaw and then spin a cocoon in which they develop into adult moths.  An interesting cycle!

So the two Woolly Bears I found last week were still looking for suitable sites to overwinter.  I hope they found something because heavy winter has since come.  With the temperature at -13ºC this morning, and about 25 cm of snow which has come since, they are likely in for the winter.  

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