Ever seen one of these caterpillars crossing the road in the fall and wondered where it is going with such a sense of purpose?
They are woolly bear caterpillars (Pyrrharctia isabella), and they are the juvenile form of the Isabella tiger moth:
You may wonder why wooly bear caterpillars put themselves at such risk by crossing roads. They are are not fussy eaters, and will eat just about anything (including dandelions, grasses, plantains, nettles and many other common wild plants), so probably they’re not searching for some kind of rare or specialized food source.
More likely is that they’re scouting around for a safe place to spend the winter. When the weather turns cold in fall, almost- fully-grown woolly bear caterpillars curl up in the leaf litter under plants and trees, or in wood/brush piles, and hibernate til spring.
Amazingly, they have adapted to survive the frozen northern winters by producing a chemical substance that protects them from freezing! A natural antifreeze…
Unfortunately for woolly bear caterpillars, hungry winter birds consider them a great protein source, so many caterpillars don’t make it through to spring. Those that survive wake up in March or April when grasses and plants start forming leaves, eat for a short time, then begin spinning a dark silky cocoon around themselves to continue the transformation into a tiger moth.
So what do you think? Why do you think the woolly bear is crossing the road? Is it looking for fallen leaves or the brushpile in your beautiful wildlife garden where it can sleep until spring?
Ellen Sousa is a garden coach and writer from Spencer, MA, where she maintains a small horse farm as NWF Certified Backyard Habitat 71074. Visit her habitat farm website and blog at THBFarm.com
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