I just finished taking pictures of our Gulf Fritillary caterpillars. They are busily devouring a small passiflora vine that I had planted last year (and took a long time coming back up this year). Strangely, I have a huge, well-established passiflora just a few feet away from the current vine that these caterpillars are on, and there are no caterpillars on that one. It seems that the butterflies are only being attracted to that one vine since it has been several weeks now (several rounds of eggs have been laid).
I did see a butterfly circling around our milkweed plants, but I was too far away to determine what it was. We will certainly be on the lookout for caterpillars on those plants too.