Queen-specific signals and worker punishment in the ant Aphaenogaster cockerelli: The role of the Dufour's gland

Chemical communication between reproductives and subordinates within social insects is fundamental to maintaining colony organization. Cuticular hydrocarbons are thought to be the dominant source of fertility signals among ants; however, differences found within the Dufour's glands could also serve as fertility signals. We investigated the function of the queen Dufour's gland in Aphaenogaster cockerelli, an ant species in which cuticular hydrocarbon profiles serve as fertility signals. The queen's Dufour's gland contents distinguish her from all other members of the colony. When she encounters a competing reproductive worker she uses her gland to mark the worker, inducing punishment from nestmates. We show that only the queen's Dufour's gland can induce the observed amount of aggression. The Dufour's gland and the cuticular hydrocarbon profile of A. cockerelli queens are both queen-specific signals, but they have different functions. The cuticular hydrocarbon profile advertises the fertility status of queens, while the Dufour's gland elicits directed-nestmate aggression towards reproductive workers. Our study also points out striking similarities in the use of the Dufour's gland that span several subfamilies and forms of colony organization in ants, leading to a task separation of queen-specific signals.