Male elimination in the honeybee

In a striking example of sex allocation modification, female social insect (hymenopteran) workers sometimes cannibalize a fraction of their colony's immature males. The commonly cited explanation for this male elimination is that workers are in genetic conflict with the queen and are biasing the colony's sex allocation in their favor. However, this behavior might allow workers to tailor their colony's investment in reproduction to environmental conditions and therefore might play an important role even in the absence of queen--worker conflict. So far, male elimination has been demonstrated only in species where the potential for queen--worker conflict is high. Here we present experimental evidence for facultative male elimination in the honeybee, a species where queen--worker conflict is expected to be minimal or absent because of multiple mating by the queen. We manipulated the abundance of older male brood in colonies and found that survival of younger male larvae was lower when we increased the abundance than when we decreased it. Survival of worker larvae was high across colony conditions. These results suggest that genetic conflict is not a necessary precondition for male elimination in social insect societies. Instead, male elimination might sometimes reflect adaptive adjustment of male reproductive function, potentially increasing colony efficiency in the interests of all colony members. Copyright 2008, Oxford University Press.