In this, and the next few articles, we will continue to explorethe social biology of the primitively eusocial wasp Ropalidiamarginata through simple experiments. Since eachwasp colonyhas a single fertile queen and several sterile workers, andsince all or most wasps are capable of taking on both roles,the wasps have to decide who will be the queen and who willbe the worker/s. Such a decision has to be made both whennew colonies are being initiated as well as when an old queenin a mature colony has to be replaced by a new one. Here, Iwill describe a simple laboratory experiment that reveals thatin the context of new nest initiation, wasps decide who will bethe queen by fighting—the winner becomes the queen and theloser/s become the worker/s. The same experiment, in additionto revealing the proximate mechanism of the division ofreproductive and non-reproductive labour, also throws lighton the advantages of such division of labour.