ONTOGENIC CHANGES IN FORAGER POLYMORPHISM AND FORAGING ECOLOGY IN THELEAF-CUTTING ANT ATTA-CEPHALOTES

In the leaf-cutting ant Atta cephalotes (L.) small colonies produce a relatively narrow size-range of small workers, whereas large colonies produce a much wider size-range of workers. In this study, I compared the foraging of four small A. cephalotes colonies (fewer than 5000 wor kers) with published data on foraging of large colonies to examine how colony size and worker size-range may be related to foraging ecology in leaf-cutting ants. I found that the foraging ecology of small A. ce phalotes colonies is very different from that of large colonies. In sm all colonies, a relatively narrow size-range of foragers (1.4-6.7 mg, mean 3.3 mg) cut primarily ''herbs'' (ferns, grasses, and other small herbaceous plants) located within 7 m of the nest. In contrast, in lar ge colonies, a broader size-range of workers (1.4-30 mg, mean 7.3 mg) participate in foraging, generally harvesting from trees 20-80 m from the nest, with larger workers cutting on trees with thicker and toughe r leaves. Small colonies' dependence on small herbaceous plants near t he nest may have a profound impact on distribution of A. cephalotes. A . cephalotes colonies are rarely found in primary forest, where the lo w occurrence of small herbaceous plants in the understory may preclude the establishment of young colonies.