between species is consistent with an “arms race” caused by conflict (Why would a good, efficient communication system need to change rapidly?). In other words, the complexity of the provisioning process may not be purposeful clockwork, but more like a boxing match full of punches and counterpunches. The winner varies from species to species, with queens producing all of the males in some and workers producing most in others (Tóth et al., 2004).
If we do not see these elaborate direct contests in other species, it may be because the stingless bees are rather unusual in mass-provisioning their brood cells with all of the food before oviposition. This focuses the laying process on one cell at a time and brings the contenders together. And of course, workers are favored to produce the males because colonies are headed by single-once mated queens (Peters et al., 1999).
In other social insects, workers have wider opportunities to lay eggs when the queen is absent. Policing by the queen then seems unlikely to succeed in colonies with thousands of workers, so one might expect workers to take advantage of this lack of control and produce many males. In some species they do, but in other species, like the honey bee, the queen still produces all of the males. Here, policing of worker-laid eggs is performed by other workers, in a seeming lapse of class solidarity. Each worker should prefer to lay her own male eggs, but how should she view the contest between other workers and the queen? When the queen is mated multiply, as in honey bees, and workers are usually half-sisters, each worker will prefer the queen’s males (r = 1/4) to those of other workers (r = 1/8) (Ratnieks, 1988). Again we have the inefficiencies of conflict, with some colony members negating what the others have done. Workers may be neuter but, to recall Paley’s adjective, they are anything but neutral. They would prefer to reproduce, but they also prefer not to let each other reproduce, and therefore they ensure that the queen wins. Oddly, the stronger the policing, the less actual conflict there may be. In species in which most worker-laid eggs are removed, few workers develop ovaries and lay eggs (Wenseleers and Ratnieks, 2006).
Workers can sometimes win the battle with queens in the most extreme way possible: by killing the queen (Bourke, 1994). Usually this is not a beneficial option, because the workers need the queen to produce both more workers and more reproductive females. But certain social insects have an annual colony cycle with males produced at the end, which makes the queen dispensable at the end of the season. Killing her allows workers to produce all of the males. Again, the choice appears to be affected by relatedness in ways predicted by kin selection theory: queens disappear more in singly mated species because those are the species in which workers favor production of males by other workers (Foster and Ratnieks, 2001).