Social Behavior in Passalid Beetles (Coleoptera: Passalidae): Cooperative Brood Care

A brief summary is given concerning passalid social behavior in relation to their life cycle.Passalid pairs defend log tunnels and remain with offspring from egg to adulthood.Parent-offspring cooperation involving care of other offspring is a step in the evolution of eusociality.Young adult passalids cooperated with their parents in repair of sibling pupal cases.Cooperative brood care between parents and juveniles has not been reported previously for non-Hymenopterous or non-Isopterous arthropods.The presence of overlap of generations and cooperative brood care by at least temporarily non-reproductive adult individuals in certain passalid species suggest that we might consider these passalids to possess one of the highest levels of subsocial behavior known for arthropods.Habitat, trophic rela-