Some of my favorite visitor in my wildlife habitat are the Butterflies.

Here is a list of some of the more popular butterflies of Pennsylvania that visit my yard and the plants needed to attract them to lay eggs.

Host plants needed for Black swallowtail butterfly larva include the following.
Dill
Celery
Water Parsnip
Marsh Celery
Wild Carrot / Queen Anne's Lace
Fennel
Parsnips
Carrots
Parsley
My wildlife habitat has Queen Anne's Lace spread throughout and I do see Black swallowtails every year.

Host plants for Monarch Butterfly larva include the following.
Any milkweed plants are acceptable for Monarch larva. This includes the entire Asclepias family. There is a lot of controversy surrounding the use of tropical milkweeds in northern climates so I tend to use native and northern types of Asclepias. Some are really nice additions to the garden and include the showier types like Purple Milkweed, swamp milkweed, and orange butterfly weed.

Host plants for Hummingbird Moth larva include the following.
Honeysucle
Rose
Plum
Cherry
Dogbane
Hawthorne
These are cool Moths that are often mistaken as Hummingbirds and are as hard to photograph as well. I have them in my yard all the time but I never seam to get any good photos of them.

Host plants for Eastern Swallowtail are mostly the same as the host plants for Black Swallowtails but also include the following.
Common Rue
Sassafras
Citrus
Common Prickly Ash
Gas Plant
Milk weed
Dutch Mans Pipe
Choke Cherry

As far as host plants for adult butterflies they need flowers that provide nectar. They will enjoy all nectar producing flowers but usually like flowers that form either clumped masses of flowers or flowers that are large with flat surfaces.