Ants defend extrafloral nectaries (nectar produced in organs other than flowers) of a passion flower vine against herbivores. This is an example of plant-animal interaction evolved in at least three levels.
 Extrafloral nectaries seen in this video resemble butterfly eggs. Butterflies avoid laying their eggs on host plants if they see other eggs. This is particularly true for two species of butterflies Gulf fritillary (Agraulis vanillae) and Variegated fritillary (Euptoieta claudia). caterpillars of these butterflies are cannibalistic. Passion flower therefore protects itself by visual trickery. Fooling herbivores by egg mimicry.
 Extrafloral nectaries attract ants. Ants are very efficient in exploiting and defending resources. Therefore Passion flower achieves another layer of protection against herbivores especially against the ones coming to eat reproductive flower parts.
 Ants are everywhere. Extrafloral nectaries distract ants away from the flowers so that pollinators can have better access.
(*) Gulf fritillary (Agraulis vanillae)
(*) Variegated fritillary (Euptoieta claudia)
(*) The green-orange beetle is Calleida punctata: