Polymorphism and size-pairing in the harvester ant Pogonomyrmex badius: a test of the ecological release hypothesis

The role of caste polymorphism in the foraging strategy of Pogonomyrmex badius was studied in the field by measuring food items collected by foragers, and correlating food item size variables with forager size variables. The diet of P. badius included seeds and insects. In two colonies examined, these food types comprised different proportions of the diet sample. Although some forager size variables showed close or significant correlations with food item size variables, we could identify no overall significant relationship between worker size and seed or prey size. Polymorphism in P. badius may be associated with omnivory. However, since minor workers serve as foragers and represent a portion of the total worker size variation, dietary expansion through caste proliferation appears to be only one aspect of the functional significance of polymorphism in this species.