The discipline of neuroethology integrates perspectives from neuroscience, ethology, and evolutionary biology to investigate the mechanisms underlying the behavior of animals performing ecologically relevant tasks. One goal is to determine if common organizational principles are shared between nervous systems in diverse taxa. This chapter selectively reviews the evidence that particular brain regions subserve behaviors that require spatial learning in nature. Recent evidence suggests that the insect brain regions known as the mushroom bodies may function similarly to the avian and mammalian hippocampus. Volume changes in these brain regions during the life of an individual may reflect both developmental and phylogenetic trends. These patterns may reveal important structure-function relationships in the nervous system.