When so large a number of the larvæ hatch out as to overcrowd the hive, it is the function of the queen to lead forth a swarm. Meanwhile several larval queens have been in course of development, and matters are so arranged by the foresight of the bees, that one or more young queens are ready to emerge at a time when otherwise the hive would be left queenless. But the young queen or queens, although perfectly formed, must not escape from their royal prison-houses until the swarm has fairly taken place; the worker bees will even strengthen the coverings of these prison-houses if, owing to bad weather or other causes, swarming is delayed. The prisoner queens, which are fed through a small hole in the roof of their cells, now continually give vent to a plaintive cry, called by the bee-keepers 'piping,' and this is answered by the mother queen. The tones of the piping vary. The reason why the young queens are kept such close prisoners till after the departure of the mother queen with her swarm, is simply that the mother queen would destroy all the younger ones, could she get the chance, by stinging them. The workers, therefore, never allow the old queen to approach the prisons of the younger ones. They establish a guard all round these prisons or royal cells, and beat off the old queen whenever she endeavours to approach. But if the swarming season is over, or anything should prevent a further swarm from being sent out, the worker bees offer no further resistance to the jealousy of the mother queen, but allow her in cold blood to sting to death all the young queens in their nursery prisons. As soon as the old queen leaves with a swarm, the young queens are liberated in succession, but at intervals of a few days; for if they were all liberated at once they would fall upon and destroy one another. Each young queen as it is liberated goes off with another swarm, and those which remain unliberated are as carefully guarded from the liberated sister queen as they were previously guarded from the mother queen. When the season is too late for swarming the remaining young queens are liberated simultaneously, and are then allowed to fight to the death, the survivor being received as sovereign.