Communication is critical to the maintenance of the often extraordinary levels ofcooperation that may occur between individuals of the same and different species. Ants are frequent partners in interspecific cooperative relationships, including with the larvae of butterflies of the family Lycaenidae (Lepidoptera). Although the costs and benefits of lycaenid-ant associations have been extensively documented, recognition and communication mechanisms are still poorly understood. It is widely thought that cuticular hydrocarbons, important for mediating nestmate recognition, may also play a significant role in initiating and maintaining cooperative behaviour in lycaenid caterpillars and their tending ants. To unravel the role of chemical signals as recognition cues in lycaenid-ant associations, we examine the larval cuticular hydrocarbons of the Australian butterfly Jalmenus evagoras and its attendant ants by targeting a variety of J. evagoras populations associated with different ant species and on different Acacia host plants. We investigate the initial acceptance of early instars by the associating ant colony by documenting ontogenetic changes in the larval chemical profile. We discuss how these patterns of cuticular chemical profiles maintain the mutualistic association between larvae and ants.