Conflict over sex ratios was an exciting finding, both because of the support that it provided for kin selection theory and because it showed that even sterile workers could find ways to pursue interests that were different from the queen’s. It thus poked a hole in the view of a colony as superorganismal, a small hole by itself, but one that opened up a vista of other realms of possible conflict. Hamilton’s rule predicts more extensive conflict over the question of who gets to reproduce. Although typically related, individuals are genetically separate, and each individual is usually more related to its own young than to those of a relative. If other things are equal, Hamilton’s rule predicts that each individual would prefer to take the reproductive role. Thus, even though advantages like fortress defense or life insurance select for helping instead of going it alone, the issue of helping is not completely resolved because it is often better, still, to be helped.
Conflict over reproduction has long been apparent to researchers working on simple social insect societies that are made up of morphologically identical females, such as Polistes wasps. Colonies are initiated by single females or by groups of females, who are often sisters. They do not share reproduction equally. Instead, they form dominance hierarchies (Pardi, 1942; West-Eberhard, 1969; Strassmann, 1981) enforced by time-consuming aggression so intense it can result in death, although some species have conventions that reduce the battling (Hughes and Strassmann, 1988; Seppä et al., 2002). Once the hierarchy is set, the losers function as workers, if they choose to remain at the nest. But they still may not work optimally, instead waiting for a chance to reproduce. In Liostenogaster flavolineata, a Malaysian stenogastrine wasp that lacks morphological castes, a queue based on order of arrival determines who succeeds the dominant queen. When females reach the number two spot in the queue, they work less hard (Field et al., 2006). In other words, when the option of reproducing directly appears more likely, they decline to take as many risks on behalf of their relatives.
The success of predictions of sex ratio conflict led researchers to ask how much conflict over reproduction remains in highly eusocial insects, those with morphologically distinct queen and worker castes. Are these colonies subject to the complexities of cross-purpose?
It turns out that even the most advanced societies are not immune to this kind of conflict. When it comes time for honey bee colonies to divide, several half-sister queens are reared with special food in extra-large cells. The old queen leaves with much of the workforce to start a new colony. Then, the first of the new queens to emerge as an adult seeks out all of the other queen cells and uses her sting to kill her sister rivals (Gilley, 2001).