The foraging ecology of the army ant Eciton rapax: An ergonomic enigma
Ecological Entomology
1985
Journal Article
10
2
131-141
Reserva Nacional Tambopata animals invertebrates arthropods insects ants army ants Eciton rapax animal behavior small spatial scales single-species study ecology feeding predation Madre de Dios Bibliography
This research was carried out in the TRZ, during the dry season, between April and September 1983. It has been observed that large groups of army ants of the species Eciton rapax organize attack systems on a markedly larger scale than other members of the genus Eciton, and they are specialized predators on ants inhabiting the undergrowth and forest floor such as species of the genera Camponotus, Odontomachus and Pachychondyla. Allometric analysis confirms that Eciton rapax is the only member of the genus that does not present physical distinctions of caste among its workers; its foraging population is entirely monomorphic, there being no differences between the individuals. The workers of this species are distributed over a considerable range of sizes, and there are clear divisions in the work they do within the colonies; small workers look after the nests, working among the large foraging workers. The latter, which are appreciably bigger than the rest, acquire prey for the whole colony. An analysis of the work and efficiency of foraging in this species indicates that the price of transportation, resulting from the great distances that the workers cover during invasions and emigrations, is one of the selection pressures which has favoured the evolution of large monomorphic workers. The division of labour in colonies of social insects is of considerable theoretical and ecological interest. Other researchers have studied the efficiency of discharge of function of the workers: the great majority of genera have monomorphic workers. It has been estimated that of the 263 genera of ants currently in existence, only 44 (16.73%) have species showing a significant degree of polymorphism in their workers.