How to Care for a Wooly Bear Caterpillar

Late in the fall or in early winter, locate a couple of dormant Isabella wooly bear caterpillars. These are the familiar fuzzy caterpillars with black ends and a russet-colored band around the middle. You'll find a dormant wooly bear curled up into a fuzzy coil in a woodpile, under leaves in the woods, near the edge of an inactive compost pile, under a rock, near a log, under a tuft of grass or anyplace that provides a natural sheltered spot. Although wooly bears produce their own antifreeze that keeps their bodies from freezing, they hibernate through cold weather, remaining dormant until warm spring weather arrives.

Place dormant wooly bears into a clean tupper-type container with a lid that seals, but don't "burp" the lid. Dormant caterpillars do not require much air; in fact, too much air flow can dry them out. There is no need to put grass or leaves in the container. The caterpillars are dormant and will not eat, and the vegetation may mold or grow fungus in the enclosed container. A clear container is good, since it allows you to visually check the little guys without disturbing them. Keep the closed container in the refrigerator for a constant temperature. Don't let the container sit out where it will warm up, or the dormancy will be broken and the caterpillars will think it is spring. If they accidentally warm up and become active, they must have fresh vegetation for food or they will die. You probably will not be able to find green, growing grass and weeds for them in the middle of winter, so take care to keep them dormant.

Keep the caterpillar container in the fridge until early plants begin growing outdoors in the spring. Remove the container, loosening the lid for air or replacing it with cheesecloth or screen, and keep it at room temperature. Put a couple of twigs, a few tender green leaves and a bit of green grass in the container in case the awakening caterpillars are hungry. Provide a supply of clean, fresh vegetation daily, and keep the container clean. The caterpillars may eat a little for a few days, but don't worry if they aren't ravenously hungry. Their purpose now is to pupate.

They will begin spinning a cocoon within a few days of becoming active, attaching it to twigs or grass or leaves. The cocoon looks like a hairy little brown mass. After a pupation period of two to three weeks, the adult Isabella Tiger Moth will emerge from the cocoon.

The adult moths are pale yellow, with small brown spots on the wings. The smaller hind wing may be slightly pinkish. The moth's body is covered with fine yellow hair, with rows of brown spots running the length of the abdomen, and three fine brown lines/stripes running lengthwise on the thorax. The adult moth's body is about 3/4 inch long, and they have a wingspan of about 2 inches. If you see Isabella Tiger Moths congregating around lights at night, they are probably males. Females don't have time to bask...they keep busy in the dark attracting males, mating, and depositing their eggs.

Sources:
Personal Experience
Bill Oehlke: Caring for Wooly Bear Caterpillars http://www3.islandtelecom.com/~oehlkew/spisabel.htm