Leaf-cutting ants make clear choices of leaves. Few experiments have demonstrated a link between the behavior of workers and the optimal needs of the ants and symbiotic fungus. This study utilizes the higher attine Trachymyrmex septentrionalis McCook as a model system to address this problem. This project illustrates the effect of forager choices on the productivity of colonies and growth of the symbiotic fungus. The former is measured by the weights and energetic content of ant offspring and the latter by a biochemical quantification of chitin, the primary compound in fungal cell walls. Colony substrate preferences were determined in pairwise trials and then replicate colonies were randomly assigned to one of two treatment groups that corresponded to preferred and unpreferred substrates. In each preference category there were two different substrates and each colony received only one type. Feedings commenced until colonies contained mature sexuals. Preferences were remarkably fixed; foragers in all colonies consistently preferred oak catkins and caterpillar frass and did not prefer flowers and leaves. While preferred substrates generally lead to large fungus gardens and high levels of ant biomass, there was significant variation among the substrates within each preference category. Preference and ant production were not correlated. Interestingly, ant production appears to be the most efficient on an unpreferred substrate. Work in progress includes quantifying the amount of fungus in these gardens.