Article by Anita Carpenter in the Wisconsin Department of Natural Resources magazine
From the October 1999 issue:
A slow crossing to Winter
The woolly bearís stripes donít predict
cold weather, but we know what makes
its coat change color.
by: ANITA CARPENTER
A woolly bear
bundled up against the cold.
© Don Blegen
Each September and October, legions of woolly bear caterpillars (Acrea
decide that the grass is greener on the other side of the highway. Humping
across the road at a fairly respectable four foot per minute pace, the furry
caterpillars, (black on both ends, reddish-brown in the middle) are blithely
unaware of the consternation they cause drivers who try to avoid them.
Why do these multitudes cross the highways? Itís more than getting to the
other side. The traveling woolly bears have finished feeding for the year and are
moving about searching for the perfect spot to curl up and spend winter under
bark, a rock or a fallen log, although I often wonder if the warm road somehow
appeals to them.
Since woolly bears are so noticeable in autumn, they have become legendary
predictors of the coming winterís severity. Folklore states that the wider the
black bands, the colder the winter. Also, some believe the hairier the critter,
the harsher the winter.
We take great interest in the woollyís winter coat, but donít give a second
thought to what the caterpillar will become. Each fuzzy, 1½ inch caterpillar
becomes an Isabella moth.
After wintering in its chosen spot, the caterpillar awakens on a warm spring
continues to feed. Soon it forms a cocoon and pupates. In about two weeks, an
orange-yellow moth with 1 ½- to 2-inch wingspan emerges. The wings lack distictive
markings but the abdomen is spotted with three longitudinal rows of small black dots.
The moths are active at night throughout summer.
Fertilized female Isabella moths lay eggs in small clusters on a variety
plants including birches, elms, maples, asters, and sunflowers. The eggs
hatch in four to five days and the tiny caterpillars begin feeding on their host
plants. The caterpillars shed their skins or molt six times before reaching adult
size. With each molt, their colors change, becoming less black and more
reddish. Thus differing colors among the caterpillars merely reflect age
differences, not an indication of impending harsh weather. Two generations of
caterpillars are produced each year, so itís the second generation that
If you try to pick up a woolly bear, it curls defensively into a tight
thick ¼-inch hairs sticking all over to dissuade would-be predators. With luck,
the woolly bear survives its cross-country journey, finds a snug place for the
winter, re-emerges in spring, and transforms into quite a different creature from
the furry little beast that crossed the road last fall.
All credit for this article goes to Anita Carpenter as
published in the Wisconsin Department of Natural Resources magazines.
All photos are credited to the contributor as seen in the article at: http://www.wnrmag.com/stories/1999/oct99/wbear.htm