They are Black Swallowtail caterpillars. They become beautiful butterflies.

Jane, here is a picture of a male Eastern Black Swallowtail. They are beautiful butterflies.

~Laura

Thank you, I figured it was some sort of butterfly. I planted one small parsley plant and they have devoured it in one day. Thats okay with me, I'll plant some more inside the porch.

What else do they eat? Its apparent they like parsley :-))

Jane

In my yard they like fennel, but I hear they like dill and carrots as well.

Dill, parsley, fennel, rue, queen anne's lace are some that I know of...

~Laura

Also Zizia, for the native plant enthusiasts.

Here is a link that might be useful: Zizia