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Woolly bears and weather lore

The larva of the Isabella tiger moth, or the banded wooly bear caterpillar as it is commonly known, is the species that folks associate with the winter weather forecast. Wooly bears are frequently seen on the roads in the fall as they seek overwintering shelter.
TRR photos by Scott Rando

October 2, 2013

Now is the time when you will likely see furry caterpillars, black with an orange stripe in the middle, crossing roads or sidewalks. These are the much celebrated “woolly bears,” or the larvae of the Isabella tiger moth. There are two generations of wooly bear caterpillars per year, and the second generation overwinters in logs or under bark. Most of the caterpillars seen in the fall are on a quest to find a suitable overwintering location.

Legend has it that woolly bears can predict the harshness of the coming winter; if the central orange band is narrow on a woolly bear, the coming winter will be harsh. In 1948, Dr. C.H. Curran, curator of insects at the American Museum of Natural History, started an eight-year experiment in which he counted orange and black segments of woolly bears in Bear Mountain State Park, NY. He found a rough correlation between wide bands and mild winters, but realized himself that the number of sampled larvae in his experiment was small. Further studies by entomologists have shown that band size varies by age and instar (molt) of the caterpillar.

There are many similar caterpillars that can be seen in the fall. They are part of the arctiidae family, which is characterized by hairy caterpillars. The milkweed tussock moth is an easily spotted example.

Woolly bears are not harmful if touched, but some arctiids, such as the Hickory Tussock Moth larva, have bristles that can inject toxin into the skin if handled; burning, itching, or worse will follow if you contact one of these critters. Most woolly bear look-alikes overwinter as caterpillars. Take a look at the images to see a few of this fall’s hairy caterpillars.