THE PERSISTENCE OF ROLE IN EXTERIOR 
WORKERS OF THE HARVESTER ANT, 
POGONOMYRMEX RADIUS 
By Deborah M. Gordon* 
Department of Zoology, Duke University 
Durham, NC 27706 
The social organization of an ant colony channels individuals into 
particular tasks, so that the colony continues to perform its tasks in a 
regular way. In other words, the colony is organized so that certain 
roles ( sensu Oster and Wilson 1 978), vital to its function, continue to 
be filled. The present study reports on role behavior in exterior 
workers of the harvester ant Pogonomyrmex badius. 
Three questions are addressed: 1) In P. badius, do particular 
groups of ants consistently do certain tasks? 2) Does the task per- 
formed by an ant depend on its age? Because P. badius workers live 
for about a year (Porter and Tschinkel 1982), marked individuals 
were observed for a longer time (up to four months) in the present 
study than in previous studies of Pogonomyrmex species (Holldobler 
1976, Porter and Jorgensen 1981). 3) Does the task performed by an 
ant depend on its size? P. badius is the only polymorphic species in its 
genus. Since majors rarely emerged from the nest, only the role 
behavior of minor workers was considered in this study. However, 
even within the minor subcaste of P. badius, a greater size variation 
exists than in other Pogonomyrmex species. The relationship 
between size and role in P. badius minors is investigated. 
In the present study, the behavior of exterior workers is classified 
into a more detailed set of tasks than in previous studies of the genus. 
Foraging, i.e. food retrieval, is only one of five activities observed 
outside the nest. The classification of tasks used here is needed to 
explain other aspects of Pogonomyrmex behavior (Gordon 1983a 
and b). 
♦Current address: MCZ Laboratories, Harvard University, Cambridge, Mass. 02138. 
Manuscript received by the editor April 24, 1984 
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