Posted by kelly Stilwell on December 4, 2005

Q: We have 4 Woolly Bears and 2 of them look like they have a white substance(looks like mold to me) on their undersides. They are not hard to the touch, so I don't think they are dead. We have tried to keep Woolly Bears through the winter with no success, but found these so late in the year we thught they wouldn't survive so why not try. So my questions are:

1. Could the white be a cocoon-or do you think they are dead?

2. Should we feed one if it is suddenly moving around after 2 weeks of "sleeping"?

3.Can they survive outside if we find them around Thanksgiving or later? Should we leave them alone? Thanks so much.

Woolly Lovers in MD

Habitat: suburban/yard

State: Maryland

Habitat: suburban/yard

A: Whenever I have a question about caring for an animal (or plant for that matter) I try to imagine or do some research about how that animal would survive in nature - what would it eat, how would it survive winter, how might it provide for its young etc. By doing this, I can then apply that information to the care of a given animal in captivity. If you do this too with your Woolly Bear caterpillars, you should be able to come up with some answers to your questions.

Woolly Bear caterpillars feed during the summer and then as fall approaches, they find a sheltered location in which to overwinter. The Woolly Bears people see crawling across the road are looking for a safe place to hibernate. Once they locate a sheltered place, they remain dormant all winter long - they do not eat or even move. When spring arrives and temperatures are warm enough, they break dormancy and change into their pupal form (they build a little cocoon out of their own body hairs) and then emerge as an Isabella Moth, mate and lay eggs for the new generation. So now, let's look at your questions.

1. The white material isn't a cocoon (remember they don't pupate until spring) and their inactivity probably means they are in their dormant phase. Your observation that the white material may be a mold (fungus) is an interesting one. Insects can and do get fungal growths on them. If you can, try to remove as much of the "white stuff" as you can without hurting the caterpillars - be really gentle. I'm guessing if your caterpillars were cold (at outside temps) the fungus wouldn't have gotten started on their bodies. You didn't say so but I'm guessing that your animals are in a warm house now!

2. There is no point in even trying to feed your caterpillars. Your animals are dormant (or should be) so they won't eat anymore.

3. Back to the "what would a caterpillar do in nature" question. Sure they can survive outside - that's where they've lived for countless centuries. In fact, your caterpillars NEED to be in a cold environment to survive. I do have a suggestion about their care. If you have an unheated garage, you should be able to place the animals in a carboard box and leave them in the garage over winter. In the spring, once temp rises for a long enough period, if all goes normally, they'll make their cocoons. At this point you can bring them into the house and then watch to see when they emerge and then release them into the wild

Hope I've helped a bit. Thanks for your well-thoughtout questions.

John Wiessinger ( December 5, 2005)