If you are certain of that caterpillar identification (it sounds like you are quite familiar with the natural history of the area!), that should certainly help narrow things down. There are only two fritillaries recorded in Miami-Dade county, the gulf fritillary (Agraulis vanillae) and the variegated fritillary (Euptoieta claudia). It sounds like the gulf fritillary may only feed on species of Passiflora, so if that’s the species of fritillary you have, it must be a passion vine. Although passion vines typically have lobed leaves, this isn’t true of all of them. P. foetida, which is listed as a host plant of the gulf fritillary, has unlobed leaves, as illustrated on this page. I not convinved that’s what you have, however, since the veination is different and P. foetida has small serrations on the leaf borders. The variegated fritillary has somewhat broader feeding habits, but none of the species listed on its page come close to what you have. None of the families listed here have vines with tendrils like yours. I checked out all the Passiflora species in Florida, and I wouldn’t say any is a very good match. Unfortunately the key identification characteristic for passion vines (and other genera in the family) are their distinctive flowers (as you are no likely already aware). Having tendrils at nodes does not occur in a lot of plants, however, and none of them is an exact match for your plant. I checked the other genera of the Passifloraceae that occur in North America, and none is a better match, either. I will try to do some more searching, but if those caterpillars are gulf fritillary, it must be a Passiflora species.

Yes, it is conundrum! In looking closely at your images, it appears that each leaf has a small pair of appendages arising from the petiole. Are those what elongate into the tendrils? Or do the tendrils arise from the leaf axils? I had assumed they were axillary, but I can’t actually see where they originate. And are those two long tendrils in the photo arising from the same leaf or different ones? Thanks.

Thanks. Having a single tendril from the axil makes a lot more sense. It may not be possible to get a specific identification given the large number of Passiflora species. However, based on this key to Passiflora species from the Royal Botanical Gardens, it looks an awful like Passiflora ligularis (species 2b), sweet granadilla: your specimen has entire leaves that match photos of P. ligularis, its stem is round (terete) rather than square and lacks wings, and I think those things sticking off the petioles are the linear glandular appendages to which the key refers. (Compare your plant to this illustration, whose associated information includes “petioles with 4-8 elongate, usually paired filiform nectaries 4-10 mm long”.) Although the Kew key is for plants from the Zambesi River in Africa, P. ligularis is native to South America and grows as far north as Mexico, so it isn’t unreasonable that it would be present in south Florida, particularly since it is known for its fruits. I’m pretty confident that’s what you have.