Both the mean forager size and the variability in forager size within colonies of ants are positively correlated with niche breadth on two dimensions-size of foraging area and diet. In colonies that feed on seeds, absolute size of the foragers is related to the size of seeds taken; in colonies that feed on insects, absolute size of the foragers is related to foraging distance. The percent variation in forager size is best correlated, for all colony types, with size of the foraging area. In island communities with fewer ant species, the mean forager size is smaller and the coefficient of variation in forager size greater. The presence of slaves was found to increase both the range of foraging temperatures and the variety of foods utilized by slave-making colonies.