ABSTRACT.Queens of two species of the ant genusMyrmicabonded to workers of the speciesM. rubraL. as the latter emerge from the pupal skin can use these workers nearly 6 months later to arrest gyne formation in sex‐competent larvae of the same species. Queens ofM. ruginodisNylander var.microgyria(Brian&Brian, 1949) are as good at this as the naturalM. rubra, but those ofM. sabuletiMeinert (of a race close toM. scabrinodis)are not. Though theM. sabuletiqueens induce normal aggression against sexualizing larvae, they are unable to prevent some or all of the workers feeding larvae as though they were queenless. However, queens from different colonies ofM. rubraadopted by queenless populations of workers in spring, control their brood‐rearing behaviour perfectly.M. rubraworkers from different colonies bring gynes to maturity from female sexual larvae at different average sizes. When workers from two such sources are mixed in equal proportions, the size of gyne larva produced after a week's culture corresponds with that of one of the worker populations; it is not intermediate in size. Also, large workers can rear larger gyne‐larvae than small workers of the same age. This is only true if the workers have been living with queens all the time from emergence as an imago to the moment the experiment was set. Size mixtures only achieve the same size larvae as a pure culture of small workers would. A possible reason for this is that small workers exclude the larger ones from the nursery areas of the