wearing a russet coat

wearing a russet coat

a woolly bear undulates 

across a blue stone

As hummingbirds and geese begin their autumn exodus, flying south for thousands of miles, the woolly bears join in their own migration, crawling on multiple feet in search of a sanctuary for winter hiberation, under a leaf, a rock, a log. 

          On the charcoal gray asphalt highway, they look like tiny black dashes. I drive slowly so I have time to dodge the intrepid caterpillars as they crawl straight across, oblivious to the man-made machines bearing down on them. It's like playing a video game, only for real. Most people don't even notice them, or if they do, they don't seem to care about squashing a lowly caterpillar. 

The funny thing is, the one I find crawling across the stones on our path (curling up defensively when I touch it) is not black, not even black with an orange band in the middle, but nearly all orange with narrow black rings on both ends.

Last year the one I found in the same location was all-black, and that was just as puzzling.

This year I discover another tiger moth larva munching on a leaf, decked out in a completely orange coat, no black bands.
          What does it mean?
          That's the same question I asked last year, when the one I found curled up under a dead leaf was attired in a bristly black tuxedo, no orange cumberbund. This year the two Isabellas in our yard apparently decided to be different from their crazy highway-roulette friends and dye their spiky hair orange for Halloween.
          Entomologists claim that the number of orange hairs tells the caterpillar's age, that is, how late it emerged in the spring. We did have a hard winter and a late spring, so perhaps that does explain my pumpkin-orange specimens. But why are their dogged relatives on the highway black? 
          Enigmas bristling with mystery.

woolly bear -- black hair

woolly bear -- black hair

curled in a ball under a log

waiting for winter

Isabella usually goes with the black and orange look for Halloween, but this year she dyed her spiky hair all black. I found her curled up under a log, taking a nap.
          Isabella is a woolly bear caterpillar, and she's not the only one to change her costume. Every single one of the woolly bears I've seen crossing the highway in search of a hidey-hole for the winter have all-black bristles. In all my years of watching woolly bears, I've never seen anything like it. What does it mean? 
          The woolly bear, which is neither a bear nor woolly, is the bristly larva of the Isabella tiger moth. The caterpillar has 13 segments, normally orange-brown in the middle and black on both ends. According to legend, the wider the brown band, the milder the coming winter, so no brown at all would predict a really hard winter. But is it true?
          According to Mike Peters, an entomologist at the University of Massachusetts, the number of brown hairs indicates the age of the caterpillar, reflecting how late it emerged in the spring. A heavy winter or an early spring the previous year would result in a wider brown band. If that's true, then we should have had a harsh winter last year, but actually it was fairly warm with little snow, unlike most winters in Iowa. 
          So who knows, maybe the woolly bears just wanted a new look this year.

banded woolly bear

banded woolly bear

searching for a place to hole

up for the winter

My father is raking leaves and my sister and I are jumping into the fragrant piles. In the dry grass I find a woolly bear, steadily making its way across the yard. I pick it up and it curls into a black and orange ball, its fur prickling my palm. When I show it to my father, he tells me the caterpillar is looking for a place to hibernate for the winter, maybe under a log or a rock. He says you can tell how long and cold the winter is going to be by the orange banc on the caterpillar, the thicker the band, the milder the winter. This one has a narrow copper band. "Does that mean we'll have a lot of snow?" I ask hopefully. Then I start to worry that the woolly bear, even with a thick coat, will freeze. My father, a chemist, explains that the caterpillar produces a kind of antifreeze, like the ethylene glycol we put in our car or the propylene glycol they put in ice cream to keep it from forming ice crystals. "Maybe it's dimethyl sulfoxide," he mutters. I know that stuff. That's the liquid he puts on my skin when I get a bruise, claiming it will make it heal faster, but it still takes a long time to turn from purple to yellow. 

          We do have a lot of snow that winter, but it has nothing to do with the width of the woolly bear's band. My father's mixture of fact and fiction was misleading. He was right about the caterpillar producing a cryoprotectant. But perhaps because he wasn't a biologist, he didn't know that hatchlings from the same clutch of eggs, like kittens from the same cat, vary a lot in color, and that the copper band gets wider with age. The banded woolly bear is the larva of the Isabella tiger moth. In the spring the caterpillar emerges from hibernation, devours herbs and forbs, pupates and turns into a lovely golden moth with a furry head. The moth lives through the summer, mates, and the female lays eggs which hatch in the autumn.

          It's October and the woolly bears are migrating. I see them by the dozens, marching slowly but steadily across the highway. They always go straight across, but in both directions. I drive slowly, my eyes straining to see the tiny black caterpillars against the dark pavement. When I spot one, I swerve to miss it, making sure there's no one behind me who might wonder what's wrong with me. Today, when I stop at the mail box, I see one crossing the concrete apron before the bridge and I run back to take its picture. Before I can reach down to pick up the woolly bear and deposit it in the grass, a big truck comes down the hill, so I jump back to the shoulder. After it passes, I walk back out to rescue the caterpillar, but alas, it has been smashed flat by the wheels of the truck, its green blood spewed across the concrete.

          I feel terrible because I took its picture instead of rescuing it first. I try to console myself by recalling the story about the saint and the dead cat. A mischievous man decides to test the reputed equanimity of the saint. He invites the saint to his house for a meal, then leads him by the most unpleasant path. They come upon a cat that has been overtaken by a bus. The mischievous man says, "Oh, how horrible!" But the saint says, "See, what pearly white teeth."