Many tropical plants are categorized as myrmecophytes (ant-plants, 415 species known worldwide, Benson 1985), which have specialized structures for housing ant colonies. Ants defend their host plant against herbivores and competitors (Fiala et al. 1989) and both plants and their symbiont ants depend on each other for their survival. However, the ultimately high species-to-species specificity in the Macaranga-Crematogaster system is exceptional among myrmecophytes (Fiala et al. 1999). The genus Macaranga Thou. (Euphorbiaceae) includes about 250 dioecious shrub and tree species with a paleotropic distribution pattern, with its center of diversity in New Guinea and Borneo.

The specific partner-ants receive all resources they require exclusively from their host-plants throughout their life-cycle whereas host-plants may be recolonized after loosing their ant partner (Feldhaar et al. 2003) and may survive short periods without protection by partner-ants. 

The most crucial moment of this obligate association is the beginning as the two partners have to come together in each successive generation to establish the association anew. As nuptial flights of specific partner-ants are usually nocturnal (B. Fiala and H. Feldhaar, personal observations) volatile compounds of potential host-plants may play a crucial role as olfactory cues in host-localisation over longer distances. 

The aim of the this study is to characterize the chemistry of the blends of leaf volatile compounds of Macaranga species in order to identify the compounds in the bouquet and to obtain insights into the basis for the specific attraction of ants by their host species. However, it is also possible that non-myrmecophytic Macaranga species use leaf volatiles as chemical defence against herbivores.