celebrating nature through fine art photography (TM) - by Lloyd Paul Aiello

As the warmth of summer gradually fades away and the days become ever shorter, the spectacular colors of autumn spread across the North Eastern United States. Brisk fall weather heralds the challenges of the coming winter and the tribulations of the months to follow.

It is also the time when the Isabella Tiger Moth (Pyrrharctia isabella) caterpillar begins its hunt for a protected sanctuary in which to pass the winter.  Found throughout North America except in most northern Canada, they will usually settle under a section of tree bark, a rock, or a log.  Here they will produce a natural organic antifreeze that, along with their heavy coat, permits then to survive cold winter temperatures as extreme as -90^o Fahrenheit!

The timing of their travels and their distinctive banded coloration has led to a robust folklore of their being an established predictor of the severity of the winter to come.  The caterpillars go by many names: Wooly Worm, Fuzzy Bear, Hedgehog Caterpillar and the Entomological Society of America approved Woolly Bear. 

In this image, and as also shown here, a Wooly Bear searches the bark of a Northern White Cedar (Thuja occidentalis) in northern Maine for a suitable location in which to pass the winter.  As just barely visible in the top black region of the caterpillar, Woolly Bears have tiny eyes and limited vision.  A close-up crop of this image showing the light reflex of the left eye is shown here.  The caterpillars have 13 body segments and have generally passed through 6 larval stages by the time they are observed in the fall.  During this time, the color and size of the caterpillar’s bands change leading folklorists to postulate on how these attributes may predict the coming winter weather.

According to folklore:

• The more black on the caterpillar, the more severe the upcoming winter.
• The longer the black bands, the longer the upcoming winter.
• If the head is dark, the beginning of the winter will be severe.
• If the tail is dark, the end of the winter will be severe.
• A thicker coat means a colder winter.
• If the caterpillar is traveling north, the winter will be mild.
• If the caterpillar is traveling south, the winter will be cold.
• And since the Woolly Bear’s 13 body segments could correspond to each of the 13 weeks of winter – each week of the winter can be forecast!

Scientists have shown that the coloration of the Woolly Bear is a result of its age, species and diet.   A more favorable growing season for the caterpillar results in a narrower red-orange middle band.  As the caterpillars molt, their colors change, acquiring more black and less red. In addition, the Wooly Bears were the first insect shown to self-medicate – when they are infected by parasitic fly larvae they will ingest alkaloid-laden leaves that kill the fly larvae and cure the caterpillar. However, if the Woolly Bear eats too many of the poison leaves, they can die themselves.

With warmer temperatures in the spring, the caterpillars start feeding again and then spin a fuzzy cocoon from which they later emerge as the orange-yellow Isabella Tiger Moth with a 2 inch wing span.  The female moths will lay their eggs on a variety of low herbaceous plants upon which the young caterpillars will feed once they hatch.  Each season there are 2-3 generations of caterpillars, with only the last ones wintering over as the Wooly Bear.

So if you feel the chill of a cold and dreary midwinter day, consider the plight of the poor Wooly Bear – and each autumn may all your Wooly Bears be red and travelling north – unless of course you are a winter enthusiast!

Lloyd Paul Aiello

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