SOCIAL RESILIENCE IN INDIVIDUAL WORKER ANTS AND ITS ROLE IN DIVISION-OF-LABOR

This paper extends the notion of spatial efficiency in the organization of social insect colonies. We demonstrate for the first time that ants (individually marked workers in three colonies of Leptothorax unifasciatus (Latr.)) are not only faithful to particular positions within the nest, but they also quickly readopt these positions, relative to one another, when the colony emigrates to an entirely new nest site. This phenomenon, which we term social resilience, has implications for the role of learning in the maintenance of an efficient division of labour to which, in part, the great ecological success of social insects has been attributed. As we demonstrate with observations of another three colonies over a period of six months, workers change their positions asynchronously and different age cohorts are intermingled. Thus the reconstruction of colony spatial order cannot be accounted for by age-based task allocation (i.e. age polyethism), as at any one time the colony meshwork represents a heterogeneous mixture of different generations. These findings also show that ant colonies have a much more precise spatial structure and greater cohesion than previously assumed, and demonstrates the importance of detailed quantitative examination of the sociogenesis or developmental biology of these societies.