Re: I found a caterpillar and it has now made a cocoon

Dear Rachel,

I looked all over to try to learn the identity of your caterpillar. Unfortunately, it's very hard to recognize the species of a butterfly or moth when it's still a caterpillar. Usually scientists need to examine the caterpillar under a microscope or know the species of plant that it was eating in order to correctly identify it.

When I could not find a caterpillar that I thought matched your description, I called one of my friends, Nancy Breisch. She's one of the best entomologists I know. (Entomologists are people who study insects.) I read your description of your caterpillar to her, and she has a guess at its identity. She thinks it may be a Black Swallowtail. Swallowtails are very pretty butterflies. For more information on (and pictures of) Black Swallowtails, check out the University of Minnesota's Extension Service web site, which also has information on attracting more butterflies to your yard.

She also said that it should take a couple of weeks for the adult butterfly to emerge from the cocoon. When it does emerge, it'll be very important for the butterfly to have plenty of branches to hang up-side-down from. After it emerges, butterflies need to stiffen their wings. To do this, they hang up-side-down from a branch and let gravity pull their soft wings straight. After hardening, the butterfly will flap its wings, and then prepare to fly away. Having plenty of room available is also important. If there isn't enough room for the butterfly's wings, they won't harden straight, and then it might not be able to fly.

I also asked my friend what she used to identify caterpillars. She highly recommended reading the Golden Guide series for nearly any kind of identification, from fishes and frogs to insects and planets. She started collecting these guides and reading them when she was about your age. The Golden Guide series has one book on common American insects as well as one with information specifically about common American butterflies and moths.

I hope you enjoy watching the caterpillar transform itself into an adult butterfly. If you have any other questions about butterflies, or observing different insects, please don't hesitate to ask us!


Thank you for your question,

John