Why are they doing this?

According to Dr. Dewey M. Caron, author of "Honey Bee Biology and Beekeeping" many attempts have been made to determine what causes swarming. Beekeepers wil provide you with any number of methods to prevent their bees from swarming; mostly without good success rates. According to Dr. Caron, events have been correlated to swarming, but the ultimate factor or factors are not completely known. Strong, healthy colonies swarm. Other factors that seem to be involved in swarming are weather, day length, genetics, age of the queen, queen pheromones and physical crowding. There may be others. It is known that colonies headed by young queen are less likely to swarm than those headed by queen 12 months old or older. The mass of bees fill their honey stomachs prior to leaving the original hive. This and the fact that they do not have a hive to defend makes a swarm of bees quite docile. In flight, the mass of bees can extend 50 to 100 feet in diameter and 6 to 20 feet high. Although the queen does not lead a swarm, one must be present for the swarm cluster to remain and not return to the original colony.

(Photo by Harry Hillard)