Abstract: Reproductive division of labor between queens and workers in insect societies often relies on a complex system of selfrestraint and mutual policing. After queen loss, workers of many social insects quickly begin to produce their own sons from unfertilized eggs. In the ant Temnothorax crassispinus (Karavaiev, 1926), reproductive division of labor among workers in queenless colonies is maintained through the establishment of social hierarchies in which only top-ranking workers start to reproduce. Here, we investigate, which factors determine whether a worker becomes dominant or not and how many workers per colony lay eggs. Dissection of more than 3300 individuals from 44 colonies showed that workers with above-average mesosoma length and / or a higher number of ovarioles per ovary ("intercastes") tended to have better developed ovaries than other workers. The number of egg layers increased slightly with colony size, and up to seven workers per colony had elongated ovarioles with large, maturing oocytes.