BEHAVIORAL FLEXIBILITY OF TEMPORAL SUBCASTES 
IN THE FIRE ANT, SOLENOPSIS INVICTA 
IN RESPONSE TO FOOD 
By A. Ann Sorensen*, T. M. Busch, and S. B. Vinson 
Department of Entomology, 
Texas A & M University, College Station, Texas 77843 
Introduction 
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 physi- 
ology, 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; Rosch 1930) and ants 
(Ehrhardt 1931; Dobrzanska 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 allome- 
try 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 
*Present address and correspondence: A. A. Sorensen, Department of Agriculture, 
Agricultural and Environmental Science Program, P.O. Box 12847, Austin, Texas 
78711 
Manuscript received by the editor May 10, 1984. 
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