SummaryWhen ripe queen cells (9–10 days after grafting) were placed into queenright colonies, only 15% (0–39%) of the resident queens were replaced by a new queen. New queens reared in the queenless half of a temporarily divided colony replaced 50% of the resident queens when the colonies were re-united. Of the queenless control colonies, 90% were successfully requeened by the queen cell method.