Colonies of honey bees, Apis mellifera, from two patrilines (cordovan and dark) were established and observations were made on the behaviour shown by the worker bees in rearing queen larvae within their colonies. The relationship among the bees within these colonies was either r = 3/4 (super-sisters) or r = 1/4 (half sisters). The worker bees showed preferential care to the queen larvae that were of their own patriline. Workers of the cordovan patriline showed a stronger preference for larvae of their own patriline than did the dark workers. Cordovan workers also showed a higher rate of visitation, indicating behavioural differences between the patrilines. These results suggest that kin selection is operating on honey bee behaviour used in rearing reproductives.