Polyethism and the adaptiveness of worker size variation in the attine ant Trachymyrmex septentrionalis

Division of labor was studied in colonies from Long Island and Florida populations of the fungus-gardening ant Trachymyrmex septentrionalis. Workers showed age polyethism and a weak size polyethism, and these patterns of division of labor were not different in colonies from the two populations. Individual workers had repertoires comprised of three to five roles but tended to concentrate their labor within a single role. The data are consistent with the hypothesis that worker polymorphism and the elaboration of size-related behavior in the attine ants evolved along with the use of fresh vegetation as the fungal substrate. The data do not support the hypothesis that size variation in colonies of T. septentrionalis evolved to promote efficient division of labor. Division of labor within the worker caste is based mainly on age and appears to be an attribute of the species rather than an adaptation to a particular habitat.