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Woolly caterpillars are the larvae of tiger moths. The orange and black woolly bear -- the young of the Isabella tiger moth, Pyrrharctia isabella -- is the most well-known. They're popularly captured and raised by schoolchildren all over North America. They eat a very wide variety of herbaceous plants and grasses, and the leaves of a few trees. The adult moths eat nothing. They survive only a few days, hopefully long enough to mate and reproduce.
Woolly Bear Life
Woolly bears hatch twice a year: once in the spring, and again in the fall. Spring bears eat all summer and change into moths before winter. Fall bears eat a little, hibernate, eat some more and turn into moths in the spring. Woolly bears in the arctic, where summers are extremely short, need more than a year to grow big enough to pupate, and may live for many years as caterpillars before they turn into moths.
Herbaceous plants, also called forbs or broad-leafed plants, are any low-growing, seed-bearing plants with leaves instead of blades. They include almost anything that isn't a grass or a tree. Woolly caterpillars prefer to feed on lambs quarters, violets and clovers. They also eat dandelions, nettles, sunflower, burdock, yellow and curly docks, and most wild plants. They occasionally feed on garden plants as well, including spinach, cabbage, other greens, asters and garden herbs.
Grasses, Grains and Forbs
Woolly caterpillars seem to prefer forbs but will also eat grasses. Their diet may include any wild grasses as well as the leaves of cultivated grains including corn and barley. These caterpillars eat the actual leaves, not the stems or flowers, so they need grasses in their leafy green stage, not their fruit-bearing straw or hay stage.
Trees and Tannins
While woolly caterpillars usually stick close to the ground, they will sometimes take to the trees to feed, especially if they hatch near the margin of a woodland instead of in a pasture or prairie. They eat broad-leaf deciduous tree foliage and seem to prefer "sweeter" tree species whose leaves have fewer tannins. They feed preferentially on maple, elm and birch. They rarely bother cultivated trees, such as apples and other fruit trees, or landscaping plants, though they have been known to feed on them in conditions whereby their normal food sources are exhausted.
- Woolly Worm Festival: About Woolly Worms
- University of Illinois Extension: Wooly Bear Caterpillars and Weather Prediction
- What Do Caterpillars Eat: What Do Wooly Bear Caterpillars Eat
- Ohio Department of Natural Resources: The Wonderful Wooly Bear Caterpillar
- Encyclopedia of Life: Pyrrharctia Isabella - Isabella Tiger