Olfactory discrimination of age-specific hydrocarbons generates behavioral segregation in a honeybee colony

The functioning of a honeybee colony relies on the coordination of colony activities via inter-individual interactions. While the structure of this interaction network keeps the young individuals relatively isolated from the rest of the colony, there are two possible mechanisms that can generate this organizational immunity. A spatial segregation that restricts the young bees to the center of the colony can shield them with equal effectiveness as a behavioral segregation in which old bees choose to interact with young bees less frequently. We test the role of these two mechanisms by determining the interaction frequency between different age groups and testing their con-elation with the olfactory sensitivity of different age groups to the cuticular odor of each other. Young bees were found to interact with bees of all age groups with equal frequency, which correlates with their lack of olfactory bias for any specific age, while old bees interacted more with other old bees, which correlates with their higher olfactory sensitivity toward the cuticular odor of old bees. The distribution of olfactory responsiveness was found to be positively skewed for old bees, which provides a mechanistic basis for the heterogeneous connectivity of the interaction network observed in an earlier study. As old bees are more likely to be responsible for introducing a potential disease into the colony from the outside and spreading it via the interaction network, these results suggest that behavioral segregation, mediated by olfactory discrimination, plays an important role in generating the organizational immunity within the honeybee colony.