Some insects possess neuropeptides (inotocins) that are related in sequence and function to the mammalian oxytocin/vasopressin system. These phylogenetically ancient peptide hormones have a broad physiological function, affecting mainly water homeostasis and reproduction, but are also important regulators of learning, memory and complex social behaviors. They therefore play vital roles in both individual physiology and group living of social animals. We have teamed up to study both aspects in ant societies, in which we have recently discovered components of this signaling system for the first time in social insects, as the honeybee noticeable lacks this system. Ants therefore provide a unique model system to study not only the physiological role of this neuropeptide system for individual ants, but also how it may affect group living in eusocial insects in comparison to the well-studied societies of mammals, including humans. We will combine genome data analysis, biochemical and pharmacological characterization and gene knock-down experiments to study the diversity and functionality of this unexplored neuropeptide system in ant physiology. We will further perform behavioral observations to elucidate how these neuropeptides may affect colony reproductive patterns and social interaction networks. By this overarching approach we aim to uncover the role of this neuropeptide system in social insects, both at the individual and society level.