Division of labour in the Matabele ant Megaponera foetens (Fabr.) (Hymenoptera Formicidae)

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Abstract
Mated workers are absent in colonies of Megaponera foetens and reproduction is carried out exclusively by a lone queen. The worker caste is polyphenic with a continuous, bimodal frequency distribution of body sizes. Since physical and temporal polyethism was continuous, only one caste could be distinguished in the workers, and the boundaries of subcastes were arbitrary. The origin of polymorphism in this species may be related to its dietary preference for socially defended prey. M. foetens has 30 behaviours that contribute to colony labour. Most are executed without interaction between colony members, but foraging raids show indirect co-operation. Physical polyethism is due to size matching between the workers and the objects with which they work, especially brood stages, and is caused by purely physical constraints on workers' efficiencies in executing different tasks imposed by their various sizes. Allometry of the mandibles allows them to serve different functions in ants of different sizes. Age polyethism follows the general pattern found in other ants, but each subcaste shows elision of the tasks to which the size of the workers is unsuited.