Females lay thier eggs on the underside of leaves...then the cats feed on the plant...then they form their chrysalis and when the adult butterfly emerges they feed on the nectar of the flowers. Other hosts plants in the carrot family include: Parsley, Dill, Fennell which you probably wont have in your meadow :)

Vera

Queen Anne's lace is quite invasive. I spend a lot of time trying to get rid of it. It will spread everywhere.

A nice native host plant for the Black Swallowtail butterfly is the Zizia. There are 3 species native to your area. Common names vary, but most often they are called Alexanders or Zizias.

Here is a link that might be useful: Zizia