This black form female tiger swallowtail has been spending hours nectaring on my White Profusion butterfly bush for the past couple of days. She's huge, probably 7" across! I've been seeing a male, too, but he hasn't nectared in my garden, at least not that I've seen - he's big, but not as big as she it. I hope the female will lay some eggs down low enough that I can find the eggs or cats!
Here's a picture of the big gal - maybe the male will nectar so I can get his picture, too!