Do rebel workers in the honeybee Apis mellifera avoid worker policing?

A recent study showed that worker larvae fed in a queenless colony develop into another female polyphenic form—rebel workers. The rebel workers are more queen-like than normal workers because they have higher reproductive potential revealed by more ovarioles in their ovaries. However, it was unclear whether eggs laid by rebel workers avoided worker policing. Worker-laid eggs are normally eaten by other workers in a queenright colony. The aim of this study was to compare the survival of three classes of eggs, namely, those laid by normal workers, rebel workers, and the queen. All eggs were tested in queenright colonies. We expected that rebel workers would avoid policing by laying more queen-like eggs. Contrary to our expectations, eggs laid by rebel workers were eaten by other workers, as were eggs laid by normal workers, and only a few worker-laid eggs (both normal and rebel) survived for more than 3 h. Therefore, in a queenright colony, eggs laid by rebel workers do not avoid policing.

Social enforcement depending on the stage of colony growth in an ant

Altruism is a paradox in Darwinian evolution. Policing is an important mechanism of the evolution and maintenance of altruism. A recently developed dynamic game model incorporating colony demography and inclusive fitness predicts that, in hymenopteran social insects, policing behaviour enforcing reproductive altruism in group members depends strongly on the colony growth stage, with strong policing as the colony develops and a relaxation of policing during the reproductive phase. Here, we report clear evidence supporting this prediction. In the ant Diacamma sp., reproduction by workers was suppressed by worker policing when the colony was small, whereas in large, mature colonies worker policing was relaxed and worker-produced males emerged. Conditional expression of traits can provide strong empirical evidence for natural selection theory if the expression pattern is precisely predicted by the theory, and our results illustrate the importance of intracolony population dynamics in the evolution of social systems.