Butterflies are often prone to attack by parasites. One of the principal enemies of caterpillars are the wasps belonging to the Braconidae family. In most cases the host-parasite relationship is specific. Wasps are also known to parasite pupae of certain butterfly species. In spite of their hostile behaviour, parasites play a useful part in nature. They regulate the number of butterflies, thus maintaining an equilibrium between butterfly species and parasites.