Surface hydrocarbons of queen eggs regulate worker reproduction in a social insect

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Abstract
A hitherto largely unresolved problem in behavioral biology is how workers are prevented from reproducing in large insect societies with high relatedness. Signals of the queen are assumed to inform the nestmates about her presence in the colony, which leads to indirect fitness benefits for workers. In the ant Camponotus floridanus, we found such a signal located on queen-laid eggs. In groups of workers that were regularly provided with queen-laid eggs, larvae, and cocoons, with larvae and cocoons alone, or with no brood, only in the groups with queen-laid eggs did workers not lay eggs. Thus, the eggs seem to inform the nestmates about the queen's presence, which induces workers to refrain from reproducing. The signal on queen-laid eggs is presumably the same that enables workers to distinguish between queen- and worker-laid eggs. Despite their viability, the latter are destroyed by workers when given a choice between both types. Queen- and worker-laid eggs differ in their surface hydrocarbons in a way similar to the way fertile queens differ from workers in the composition of their cuticular hydrocarbons. When we transferred hydrocarbons from the queen cuticle to worker-laid eggs, the destruction of those eggs was significantly mitigated. We conclude that queen-derived hydrocarbon labels inform workers about the presence of a fertile queen and thereby regulate worker reproduction.