Collective Aggregation via Directed Pheromone Signaling in Honeybee Swarms*

To become a coherent swarm, honey bees (Apis mellifera L.) locate their queen by tracking her pheromones. How can distant individuals exploit these chemical signals, which decay rapidly in space and time? We combine a novel behavioral assay with computer vision for bee detection and scenting recognition to track the swarming dynamics. We find that the bees propagate the signals by creating a communication network, where there is a characteristic distance between individuals and directional signaling away from the queen. We also connect our experimental results to an agent-based model where bee agents with simple, local behavioral rules exist in a flow environment with a stationary queen. Our model shows that increased directional bias leads to a more efficient aggregation process that avoids local equilibrium configurations of isotropic (axi-symmetrical) communication, such as small bee clusters. Our results highlight a novel example of extended classical stigmergy: rather than depositing static information in the environment, individual bees locally sense and globally manipulate the physical fields of chemical concentration and airflow.