Since there is only a single female reproductive in a bee colony, there is a special procedure to replace her when it becomes necessary to do so. Replacement of a queen by another queen is a process termed supersedure. Replacement of the queen and production of another colony is another behavior which is called swarming. A third means of replacing a queen, emergency queen rearing, is necessary if the queen dies suddenly, is removed by a beekeeper, or is somehow injured or lost from her colony.
Queen failure may lead to reduced egg laying but workers more readily respond to reduced pheromone production. Each worker bee needs to receive a certain level of queen substance daily. This pheromone is distributed through food transmission among workers. If a queen is taken away, the level of this pheromone drops rapidly, though it is persistent. In the case of a failing queen, the queen produces insufficient amounts of queen substance, and therefore is fed back less of the pheromone by the bees of her retinue. This feedback system of queen pheromone distribution is vital for communication.
The first behavior change observable in queen replacement is the laying of a fertilized egg in a queen cup. Queen cups are special cup-like precursors of queen cells. They are always present in a bee colony, though their numbers are greatest in the spring months. They are built at the lower margin of beeswax comb (lower margins of frames in a beekeeper.s hive) and in spaces where the comb is damaged or left open as a walkway to the opposite side of the comb.
The queen herself places the fertilized egg in a queen cup. Worker bees can remove eggs (from queen cups or regular cells) but they are not known to transfer them. The same queen may return to the developing queen cell. (Arbitrarily, a cell occupied by an egg or developing queen is called a queen cell - it is a queen cup when empty.) By chewing on the side of the cell, the queen causes the workers to remove and kill the occupant (egg, larva or pupa) inside. It is possible to observe queen rearing repeatedly aborted in a bee colony. The original mated queen (who started the process of queen replacement by laying eggs in queen cups) may be killed before or after emergence of a virgin queen in supersedure or she may depart with a proportion of the adult workers in a swarm before a virgin queen emerges. The workers always begin to rear several new queens rather than a single one.
Emergency queen cells can be distinguished from the queen cells of swarming or supersedure because they originate from a worker cell. The horizontal orientation of the worker cells selected to be converted to queen cells is quickly changed to the vertical by enlarging the base of the cell and drawing the opening outward and downward. This usually means destroying the cell walls and removing the larvae of three to four cells adjacent to the modified cell. Capped emergency cells often seem smaller than capped queen cells started from queen cups.
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The above text is taken from The Mid-Atlantic Apiculture Research & Extension Consortium, Basic Bee Biology for Beekeepers; Fact Sheet,MAAREC Publication 1.4 March 2004. You can download this factsheet and others at the MAAREC website