Woolly worm

Woolly worms prepare for the winter season and the new life cycle to come.

Dear Naturalist,

Where do all the woolly worms go after the festival is over?

Thank you,


Dear Anna,

Woolly bears (Pyrrharctia isabella) are actually the caterpillar, or larval, stage of the Isabella Tiger Moth. As the leaves reach their peak color in mid-autumn, the woolly bear begins to seek an adequate place to spend the winter.

They are in a literal race for survival. Those that are caught out in the cold might not survive.

Once a caterpillar finds just the right spot, its biochemistry and metabolism begins to change. As its metabolism slows, the caterpillar produces glycerol — which not only reduces the amount of ice formation in the overwintering bugger, but will also protect its cells from becoming dehydrated.

The woolly worm will maintain this level of dormancy until the spring, when it will eat voraciously for a few weeks. Then it will build a cocoon from its own bristly hairs, or setae.

The diminutive adult tiger moth will emerge from its cocoon by early summer. The adults have no mouth parts and only survive for a few days. Their primary function is reproduction.

If they are successful, the whole process will begin anew, and we will have woolly worms to race next year!

If you have a question concerning flora and fauna, please email dearnaturalist@gmail.com. All of your questions will be answered. One or two will be featured next week. See you on the trails!

Amy Renfranz is a Certified Naturalist through the Yellowstone Association Institute and a Certified Environmental Educator in the state of North Carolina.

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