Woolly Bears on the Move

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Bristly "woolly bear" caterpillars have started their annual crawl-about in search of sheltered locations where they will spend the winter.  They may be found on sidewalks and walking trails or on the walls of homes and buildings.  Some may be slowly making their way to Vermillion, Ohio, to attend an annual festival held in their honor.


Woolly bears (woolly worms in the south) are the caterpillar stage of medium sized moths known as tiger moths (family Erebidae; subfamily Arctiinae).  The caterpillars are so-named because of their short, stiff bristles.  Although the bristles serve to defend the caterpillars and may look intimidating, they are not stinging (urticating) hairs.  However, some people suffer severe localized reactions if the sharp pointed hairs penetrate their skin.  Woolly bears will roll themselves into a tight ball when disturbed to bring to bear their defensive bristles.  It also makes them look like a hedgehog which is referenced by the common name of hedgehog caterpillar.


Banded Woolly Bear


There are eight or more species of woolly bears in the U.S.  Four of the most common species found in Ohio are the banded woolly bear which develops into the Isabella tiger moth (Pyrrharctia isabella); the yellow woolly bear which develops into the Virginia tiger moth (Spilosoma virginica); the salt marsh caterpillar which develops into the salt marsh moth (Estigmene acrea); and the giant leopard moth caterpillar (Hypercompe scribonia).  These moths have two generations per season in Ohio with the largest number of caterpillars occurring in the second generation.  The caterpillars of all four species may be found feeding on a wide range of plants including some field crops.


Yellow Bear Caterillar


Giant Leopard Moth Caterpillar


The banded woolly bear is the species most often referenced as a predictor of winter weather.  According to folklore, the total amount of black on the woolly bear in the fall predicts the severity of the upcoming winter:  the greater the amount of black, the more severe the winter weather.  Also, the position of the widest dark bands predicts which part of the winter will be the coldest.  If the dark band is widest at the head end, the beginning of winter will be severe.  If the dark band is widest at the tail end of the caterpillar, winter will go out like a lion.  The predictive ability of the caterpillars is further fine-tuned by "reading" the 13 segments of the caterpillar's body which are said to correspond to the 13 weeks of winter.


Researchers have debunked the weather prediction folklore by showing the amount of black varies with how long the caterpillars have been feeding and the moisture levels in the area where they develop.  Of course, caterpillar coloration also varies between woolly worm species.  If weather prognosticators use the yellow woolly bear, they would assume there will be no winter.  Conversely, the all-black giant leopard moth caterpillars could create mass panic causing folklorists to flee to the south for the winter!


Regardless, woolly bears remain an entertaining topic of late-season conversations simply owing to trying to remember the folklore!  Also, Vermilion, Ohio, has held an annual Woollybear Festival for more than four decades.  It is billed as the largest one day festival in the state of Ohio.  The festival was started by well-known Cleveland meteorologist Dick Goddard who remains a key player in the festivities.  The 44st Annual Woollybear Festival and Parade will be held this coming Sunday, October 2nd in beautiful downtown Vermilion.  For details, click on the hotlink below.