Woolly Forecaster

On a recent walk I noticed a woolly bear caterpillar (Acrea sp.) crossing the trail. These stout, hairy caterpillars (black on both ends, reddish-brown in the middle) are commonly seen on sunny autumn days and always seem to be in a hurry.

The woolly bear, unlike many caterpillars, feeds on a wide variety of plants such as grass, clover, plantain, dandelion, spinach and cabbage. As a child I was told that the woolly bear could predict the weather. The width of the rust band around its middle is supposed to tell us what kind of winter we are in for. A broad band means a mild winter; a narrow band means a winter to remember.

It is understandable why we look to animals for sign at this time of year. Winter is hard, and long. If we knew in advance how long and cold it was going to get the season might be easier to endure. But the woolly bear is not a forecaster, and cannot predict the severity of the coming winter. Actually the bands of the woolly bear tell us more about the caterpillar itself then the coming season. A young woolly bear has more black than brown. As it grows the band widens. There are two broods: one in June or July, and another in September (the ones we see in autumn.) The September brood have finished feeding for the year and are moving about searching for the perfect spot to curl up and spend winter- under bark, leaves, a rock or a fallen log. After wintering in its chosen spot, the caterpillar awakens on a warm spring day and continues to feed. Soon it forms a cocoon and pupates. In about two weeks an Isabella Tiger Moth emerges. This night flier has three rows of six black dots on the abdomen, a wingspread of almost two inches and tawny yellow wings with a few dark spots; the hind wings are sometimes tinted with dull orange.

If you find a woolly bear scurrying along a trail you can pick it up gently in your hand. Many times it will defend itself by curling into a ball. The thick ¼-inch hairs sticking all over help to dissuade would-be predators from eating the caterpillar. Eventually in response to the warmth of your hand it will uncurl and attempt to continue on it’s journey.

Fall Foliage Update 2009
Check in for weekly fall foliage updates from AMC Naturalists. We will post weekly photos from Pinkham Notch and across the AMC backcountry huts. Check back and follow fall across the White Mountains.

Sept 20, 2009 Photo from Direttissima overlook in Pinkham Notch. The colors are really starting to come out now!