My pipevine* is blooming! I still get excited by that because it took like 2-3 years at least for mine to bloom. Pipevine gets its name because the blooms look a bit like a pipe. And it is of course the host plant for the Pipevine Swallowtail. While I see many adult Pipevine Swallowtails in the summer I have yet to find any eggs on my vines.
Here are a couple pictures of the flowers from slightly different angles:
*(My pipevine page is a bit dated now, by the way. I need to find the time to update a lot on this site.)