The queen's primary role is to lay eggs and produce pheromones that regulate the colony. At her peak she can lay up to 2,000 eggs per day. Early in life she undertakes one or more mating flights, during which she mates with 10 to 20 drones in flight and stores their sperm for the remainder of her life. Until she has mated she is referred to as a virgin queen; mating takes place in drone congregation areas, specific locations where drones wait for queens to pass through.
Swarming is the natural method of colony reproduction. When conditions are right, about half the bees leave with the old queen to establish a new home, while the original colony raises a new queen. Swarm cells, the larger, peanut-shaped cells from which new queens emerge, are built on the bottom of a comb during this process. By contrast, supersedure cells appear on the face of a comb and are constructed to replace a failing queen without swarming. Triggers for swarming include congestion inside the hive, abundant resources, an aging queen, and the colony's genetics. Beekeepers can reduce the swarming impulse by adding supers for more space, making splits, removing queen cells, and ensuring good ventilation.
A split is the deliberate division of a colony into two, used to control swarming and to grow an apiary. Beekeepers also requeen colonies, replacing the queen with a new one, to improve traits such as gentleness, brood pattern, or disease resistance. Queen rearing, the practice of producing queens deliberately, often involves grafting, transferring young larvae into artificial queen cell cups. Once a new queen is produced, she must be introduced carefully. Placing her in a cage with a candy plug, a plug of hard candy that workers chew through to release her, gives the colony time to accept her. If introduction is rushed, workers may ball the queen, clustering around and sometimes killing her, which is why slow introduction through a candy plug is so important. Extra queens can also be held in queen banks, small colonies dedicated to keeping spare queens available.