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Psyche
Volume 102 (1995), Issue 3-4, Pages 131-145
http://dx.doi.org/10.1155/1995/10717

Forager Polymorphism and Foraging Ecology in the Leaf-Cutting Ant, Atta colombica

Center for Environmental Research and Conservation, Columbia University, 1200 Amsterdam Avenue, New York, NY 10027, USA

Received 17 April 1995

Copyright © 1995 James K. Wetterer.

Abstract

I compare forager size and foraging selectivity of the leaf-cutting ant Atta colombica and that of its close relative Atta cephalotes. In both species, larger foragers cut fragments of greater mass and area, and at vegetation sources of greater specific density (mass/area). However, the size-range of A. colombica foragers (1.5–56.8 mg) was wider than the range typical for A. cephalotes (1.4–32.1 mg). In A. colombica, the maxima workers (24–60 mg) commonly participate in foraging, making up 13% of all foragers in this study and in a previous study. In contrast, A. cephalotes maxima workers (24–100 mg) rarely forage (less than 1% of all foragers in two previous studies), but instead serve primarily as soldiers defending the nest. Thus, A. colombica maxima workers are smaller and do not appear to be so specialized as soldiers as are A. cephalotes maxima workers. The broader size-range of workers participating in foraging appears to allow A. colombica to exploit a wider range of resources than A. cephalotes, including tougher, denser vegetation and fallen fruits.