The factors controlling the strength and specificity of a facultative polyphilic association between a lycaenid butterfly and several species of attendant ants in different genera will be investigated. Field manipulations to determine the effect of each of the following factors on strength of association will be conducted: (1) individual phenotypic variability in lycaenid larvae; (2) variability in response by different species of ant associates; and (3) variability in host plant quality. The dynamics of facultative associations, which occupy an intermediate position between casual associations and obligate mutualisms provide a key to understanding the transitions in interaction strength. Investigation of the factors controlling the strength of facultative associations will provide information on the evolution and maintenance of mutualism. This study will also investigate whether association with ants reduces parasitism or predation of the lycaenid larva, and the possibility that various species of ant associates provide differential benefits. Specificity of the association may depend on the differential magnitude of the benefits provided by the various species of ant associates or on the dependability of encountering the various species. Determining if the strength and benefits of the association vary with the species of ant attendant will provide information on the trade-offs of the transition from polyphilic to monophilic association, and vice versa.
