One of the best plants for attracting butterflies to the garden is the passion vine (passiflora). It is the favorite food of the caterpillars of the gulf fritillary butterfly which is common to the southerner half of the United States. You must be willing to put up with some damage to the leaves while the caterpillars feast on them, but you will be rewarded with lots of lovely orange butterflies all summer.
There are many different species and colors of this vine and some of them can get very aggressive if not kept in check. I had a red one that actually scared me it grew so fast. I was afraid if I walked through the tunnel it had made over some arbors I had that I may never come out again! I ended up taking it out to allow other plants in the area to live.
This particular specie is 'Lavender Lady".