Behavioral Flexibility of Temporal Subcastes in the Fire Ant, Solenopsis Invicta in Response to Food

Most social insects are characterized by the presence of a caste system (Oster and Wilson 1978). Castes are functionally defined as any set of colony members, smaller than the society itself, that specialize on particular tasks for prolonged periods of time (Michener 1974; Oster and Wilson 1978). The performance of these tasks may be correlated with size (physical castes) or age (temporal castes) of the worker. As a rule, workers in physical castes cannot shift easily from one role to another. They tend to specialize in certain tasks predetermined by their brain structure, sensory physiology, and innate behavior patterns (Oster and Wilson 1978). In contrast, workers in temporal castes usually follow an age-related progression from nurse duties to nest duties to foraging. Studies on temporal castes in honeybees (Nolan 1924; R0sch 1930) and ants (Ehrhardt 1931; Dobrzafiska 1959; Chavin 1969; Lenoir 1979) showed that this progression is not necessarily rigid. Workers can respond to colony needs by altering either the rate or the direction of a typical behavioral sequence. In the present study, we examined the behavioral flexibility of the temporal caste system of the fire ant, Solenopsis invicta Buren. Fire ant workers are weakly polymorphic and show slight allometry with continuous size variation and three arbitrarily demarcated size categories of workers in mature colonies (Wilson 1953; 1978). Superimposed on these morphological castes is a temporal division of labor which largely determines which tasks will be performed