Beekeeping
Colony reproduction

Honey bee colonies are dependent on their queen, who is the only egg-layer. Although queens have a three-to-four-year adult lifespan, diminished longevity of queens—less than a year—is commonly and increasingly observed. The queen can choose whether to fertilize an egg as she lays it; fertilized eggs develop into a female worker bees and unfertilized eggs become male drones. The queen's choice of egg type depends on the size of the open brood cell she encounters on the comb. In a small worker cell, she lays a fertilized egg; she lays unfertilized drone eggs in larger drone cells.

When the queen is fertile and laying eggs, she produces a variety of pheromones that control the behavior of the bees in the hive; these are commonly called queen substance. Each pheromone has a different function. As the queen ages, she begins to run out of stored sperm and her pheromones begin to fail.

As the queen's pheromones fail, the bees replace her by creating a new queen from one of her worker eggs. They may do this because she has been physically injured, because she has run out of sperm and cannot lay fertilized eggs, and has become a drone-laying queen, or because her pheromones have dwindled to the point at which they cannot control all of the bees in the hive. At this juncture, the bees produce one or more queen cells by modifying existing worker cells that contain a normal female egg. They then either supersede the queen without swarming or divide the hive into two colonies through swarm-cell production, which leads to swarming.

Supersedure is a valued behavioral trait because hive that supersedes its old queen does not lose any stock; rather it creates a new queen and the old one either naturally dies or is killed when the new queen emerges. In these hives, bees produce only one or two queen cells, most often in the center of the face of a broodcomb. Swarm-cell production involves the creation of twelve or more queen cells. These are large, peanut-shaped protrusions requiring space, for which reason they are often located around the edges—commonly at the sides and the bottom—of the broodcomb.

Once either process has begun, the old queen leaves the hive when the first queen cells hatch, and is accompanied by a large number of bees—predominantly young bees called wax-secretors—which form the basis of the new hive. Scouts are sent from the swarm to find suitable hollow trees or rock crevices; when one is found, the entire swarm moves in. Within hours, the new colony's bees build new wax brood combs using honey stores with which the young bees have filled themselves before leaving the old hive. Only young bees can secrete wax from special abdominal segments, which is why swarms tend to contain more young bees. Often a number of virgin queens accompany the first swarm, known as the "prime swarm", and the old queen is replaced as soon as a daughter queen mates and begins laying. Otherwise, she is quickly superseded in the new hive.

Different sub-species of Apis mellifera exhibit differing swarming characteristics. In North America, northern black races are thought to swarm less and supersede more whereas the southern yellow-and-gray varieties are said to swarm more frequently. Swarming behavior is complicated because of the prevalence of cross-breeding and hybridization of the sub-species. Italian bees are very prolific and inclined to swarm; Northern European black bees have a strong tendency to supersede their old queen without swarming. These differences are the result of differing evolutionary pressures in the regions in which each sub-species evolved.
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