Lycaenids parasitizing symbiotic plant-ant partnerships.

Many species of the paleotropic plant genus Macaranga (Euphorbiaceae) live in symbiosis with the ant genus Cremastogaster (Myrmicinae), especially with C. borneensis. The ants protect their plants from many herbivorous enemies. The plants provide food-bodies and nesting space in the internodes. In addition the ants care for honeydew producing scale insects in these spaces. The caterpillars of several species of the genus Arhopala (Lycaenidae) parasitize on this symbiosis system. With the aid of their myrmecophilic organs the caterpillars overcome the aggressivity of the ants and feed on the Macaranga leaves without disturbance. Moreover the caterpillars and their pupae are protected against parasites and predators by the ants. As the female butterflies oviposit the eggs only in low numbers upon young leaves, the plants are not seriously affected.The larvae of the three Arhopala species; A. amphimuta, A. moolaiana, and A. zylda are adapted to their host plant species Macaranga triloba, M. hulletti, and M. hypoleuca by means of color, shape, and behavior. In addition, the different larval stages change their appearance according to the parts of the plant on which they feed and rest. These cryptic adaptations point to a distinct monophagy of these butterflies.The state of phylogenetic relationship within the three lycaenids is parallel to the relationship among the three host plants.