The precise triggers of swarming are not completely understood. One idea is that the increasing number of bees in the hive, forces some of the bees far enough from the queen that her scent is no longer detected. Queen substance is the chemical scent produced only by the queen, and is responsible for the control of a hive as a cohesive unit. Perhaps due to an aging queen producing less scent, or due to the dilution of scent among a booming population, the workers begin to construct large cells know as queen cups. The "old queen" will lay an egg in the cell as usual, but before the new queen hatches, the old queen will have left the hive. Prior to her exit, the workers will have fed the old queen less and by the time she leaves with the swarm, her weight will have dropped enough that she can easily fly. Shortly before the swarm leaves the old hive, the bees engorge with honey and scouts will leave the hive in search of a new nest site.

The departure of a swarm from a hive is a vivid, noisy and obvious phenomena. Beekeepers who do not manage their hives to prevent swarms, have often observed the dark whirling swarm of the queen and up to 80% of the bees in a hive flying off in a buzzing cloud.

The bees in a swarm are more docile, and less defensive that bees at a hive, since they are "on the move" and have no stores of honey or brood to defend.

Within minutes, the swarm will alight on a branch or some other protected spot and hang in the shape of a downward pointing pyramid. It is at this stage, that beekeepers will gladly come and remove the swarm. Swarm removal can be as simple as cutting the branch on which they are clustered, and depositing the entire mass in a large trash can. The queen is protected in the center of the swarm, and once she is in a container, the other workers will stay with her. Another method of swarm retrieval involves knocking the swarm onto a tarp, then locating the queen and putting her with a handful of bees into a new hive box. When this is done, and the lid of the hive put back on, the other workers will walk into the hive through the hive entrance!

If removal is desirable, a beekeeper should be contacted as soon as the swarm is spotted. From this first resting place, scout bees will continue to search for a new colony site. Scouts return to the swarm to perform elaborate motions over the surface to indicate the direction and location of the new hive. Usually a new location is found and the swarm leaves within 48 hours.

It is important to note, that swarms should be collected by a beekeeper if it is undesirable for bees to establish themselves in their chosen spot. In the spring or summer, it is much easier to remove bees who have just moved into a space in a wall or attic. Once the colony has established itself, the bees will be defensive to guard their honey stores, and the colony will definitely increase in size making removal far more difficult.