Brain scaling in ants: body to brain size ratio

Ants have great size diversity and are one of the most dominant insect groups in the world. Within the leaf-cutting ants of the neotropics, the genus Atta exhibits a large degree of physical polymorphism, with workers ranging in size from only a few millimeters in length to over two centimeters. We used this size diversity in Atta colombica to study the brain to body size ratio within a single species, thus eliminating phylogenetic considerations when making comparisons across species. We also examined how different neuropil in the brain scale to overall brain and body size. Although the overall brain size increases with body size the ratio is not linear. We discuss how physical constraints on brain size may influence brain structure and behavior, how overall body size may influence this ratio and how it influences division of labor. We compare our data to theoretical predictions of how brain size scales to body size.