Project Summary Humans and many other animals exhibit a wide variety of social behaviors. Traditionally, primates have been used as research models of human behavior due to their close evolutionary relationship to humans and their highly social behavior. However, the use of primates for such research has significant economic, practical, and ethical drawbacks, and, in that light, it would be useful to find other models for behavioral studies that exhibit complex social behaviors. One potential model that fits both criteria is the extensive family of insects collectively known as the ants, some species of which exhibit highly complex “eusocial” behaviors involving a strict division of labor between sterile workers and reproductive queens. Among ant workers, there is a further division of labor, with different tasks allocated among different castes of workers. Our hypothesis is that caste/colony-specific aggression and social hierarchy reflect and in-part are determined by chemosensory programs dictated largely through odorant receptors and shifts in neuropeptidomic profiles. We will investigate this question in two ant species—Camponotus floridanus and Harpegnathos saltator—that exist in large colonies that are composed of just a few males, and the remainder are females, including one (typically) queen, and numerous workers that engage in caste/colony specific aggressive behaviors such as defense, policing and dueling.