That's an excellent book to ID general groups.

What you then need to do is to investigate further the group your cat belongs to. Computer searches can work wonders.

Are you finding these caterpillars in the woods, or in your garden?

And, what are your criteria for preserving a caterpillar you might find? What determines if a caterpillar is 'a nasty', in your opinion? I value what you have to say here, because so many people don't even think about it!

Do a google on Caterpillars of Eastern North America by Wagner. It's a pretty comprehensive field guide to butterfly and moth larvae. You might also post this question in the Butterfly Gardening Forum for some good recommendations, hard copy as well as web sites.

Attached is a link which lists several good web sites for identification purposes.

Here is a link that might be useful: Click here

Rhizo1, last year arounnd fall, I discovered lots and lots of caterpillars on the passionflower vines I'd planted in with the star jasmine. It turned out to be gulf fritillary cats. I let them eat to their hearts content! In fact, I planted several passionflower vines so they might consider our yard a haven . The winter was very cold, and I do not know if any of the larva survived that, but this year I'm watching for more such larva.

I like to plant the hosts for different butterflies, such as the milkweed plants that grow here, and I do seem to have many butterflies frequenting the yard. I had a book about butterfly gardening, showing the host plants, and the nectar plants, and I want to make sure before I "do in" a cat that it is not something spectacular.

My criteria for a 'nasty' is gypsy moth or cabbage moth or some other veggie eating borer...because we do plant squash and cukes in my DH's veggie garden. You know, I did not realize that GW had a butterfly gardening forum, so I will take a run at that spot too.
Thank you for the link to the Butterflies and Moths of N.A. I would not want to be an indiscriminate destroyer of nature. Might as well have plastic plants if I was.

Good for you! The more time you spend learning about these (and other) insects, the better job you'll be able to do at attracting them and creating good habitats.

I'm a lover of moths and butterflies, but I don't plant a lot of host plants on purpose. Nectar plants galore, but I also have an abundance of birds in my gardens and don't want to set up a smorgasbord for the birds, if you know what I mean. I do keep a stand of milkweed for the monarchs (which birds won't eat) and allow the Giant Swallowtails to lay eggs on my seedling citrus.

Of course, I have assorted caterpillars nibbling on this and that, but never enough to annoy me too much.