There are three castes of bees: queens, which produces eggs; drones or males, which mate with the queen; and workers, which are all non-reproducing females. The queen lays eggs singly in cells of the comb. Larvae hatch from eggs in 3 to 4 days and are fed by worker bees and develop through several stages in the cells. Cells are capped by worker bees when the larvae pupates. Queen and drones are larger than workers and require enlarged cells to develop. Queens complete development in 15.5 days, drones in 24 days and workers in 21 days for larvae and pupae stages. Only one queen is usually present in a hive. New queens develop in enlarged cells by differential feeding by workers when the existing queen ages or dies or the colony becomes very large. Virgin queens fly on a nuptial flight. New colonies are formed when queens leave the colony with a large group of worker bees, a process called "swarming." The first or prime swarm generally goes with the old queen. As soon as the swarm is established as a new colony, the bees raise a new queen, or sometimes a replacement virgin queen is already present in the swarm. Afterswarms are usually smaller and are accompanied by one or more virgin queens. Sometimes a hive will swarm until it is almsot totally depleted.
Swarms of bees sometimes frighten people, though they are usually not aggressive at this stage of their life cycle. Most swarms will move on and find a suitable nesting location in a day or two. Beekeepers are sometimes called to capture swarms. A queen may live three to five years; drones usually die before winter; and, workers may live for a few months. A colony may typically consists of 20,000 to 50,000 individuals.