Size and behavior in ants: Constraints on complexity.

In this paper I investigate the behavioral complexity of ants in relation to brain size. The volume of the corpora pedunculata, involved in the selection of motor programs, and the antennal lobes, involved in processing olfactory information, are directly related to the volume of the brain of an ant. The volume of the optic lobe, involved in visual processing, is not related to total brain volume. Brain volume is allometrically related to head width in ants. Behavioral complexity, as assayed by the size of the behavioral repertoire within the nest, is directly related to the cube of head width. Behavioral complexity is thus related to the 3/2 power of brain volume. The size of the behavioral repertoire does not appear to correlate with any ecological characteristics of the species but may be a passive consequence of body size. Determination of body size by numerous ecological factors may place constraints on the complexity of behavior that an ant can achieve.