Forager size of the leaf-cutting ant Atta sexdens (Hymenoptera : Formicidae) in a mature eucalyptus forest in Brazil

We determined the size characteristics of foragers of the leaf-cutting ant Atta sexdens in a mature eucalyptus Forest in Campos dos Goytacazes. Rio de Janeiro State, Brazil, at daytime (7: 30 to 10: 00 hr) and nighttime (19: 00 to 23: 00 hr). There were no significant differences between daytime and nighttime ant mass (M-a), but leaf fragment mass (M-l) and burden (B = [M- a + M-l]/M-a), which indicates relative load capacity, were significantly g reater at daytime. There was a positive linear relationship between M, and MI for the combined daytime and nighttime data, and increases in M resulted in lower B. We compared A. sexdens characteristics with published results for Atta cephalotes, a closely related species. A. sexdens is larger and th erefore able to carry heavier loads, but its burden is about 72% of the ave rage value for A. cephalotes. We suggest that the lower load capacity of A. sexdens in comparison to A. cephalotes is related to its relatively larger size.