Which butterflies use the plants as a host?
Passionflower is the host plant for gulf fritillary and zebra longwing caterpillars. Gulf fritillary caterpillars are bright orange with black spines. They can become very numerous and if left unchecked they can defoliate passionflower vines. While spraying with pesticides is not a good idea, as butterflies are a desirable addition to any garden, you may wish to occasionally handpick or relocate some caterpillars to control the population, thereby keeping your plant a viable food source for the others.