Flexible task allocation and raid organization in the termite-hunting ant Megaponera analis

Abstract

Division of labor is one of the main reasons for the success of social insects. Worker polymorphism, age polyethism and work division in more primitive ants, such as the ponerines, remain mostly unexplored. The group hunting, termite-specialist Megaponera analis conducts raids in column formations of 200–500 ants. Since these ants specialize on a defensive prey, adaptations to reduce their foraging costs can be expected. We found that the work division, task allocation and column formation during the hunt were much more sophisticated than was previously thought. The column-formation was remarkably stable, with the same ants resuming similar positions in subsequent raids and front ants even returning to their positions if displaced in the same raid, suggesting yet unknown regulatory mechanisms for the formation of the column. We identified three previously undescribed tasks during the hunting process of M. analis: lingerers, runners and raid-guards. Most of these tasks were not executed by predetermined members of the raid but were filled out as need arose during the hunt, with a clear preference for larger ants to conduct most tasks. The plasticity of task allocation was particularly well exemplified by the termite carriers, with the number of small ants carrying termites only starting to rise when less large ants were available. We, therefore, propose that the continuous allometric size polymorphism in M. analis allows for greater flexibility in task allocation, necessary due to the unpredictability of task requirements in an irregular system such as hunting termites in groups.