Honey bees are valuable and provide tremendous benefits, specifically pollination, honey and wax. However there are times and places where honey bees create an annoyance and a nuisance, and for sting-sensitive individuals, a health threat. One such incidence is when honey bees swarm.
Swarming is a natural part of the development of a honey bee colony. Swarming is a method of propagation that occurs in response to crowding within the colony. Swarming is an advantage to the bees but is a distinct disadvantage for beekeepers. Consequently, beekeepers manage hives to reduce the incidence of swarming to the extent possible. Swarming usually occurs in late spring and early summer and begins in the warmer hours of the day.
Honey bee swarms may contain several hundred to several thousand worker bees, a few drones and one queen. Swarming bees fly around briefly and then cluster on a tree limb, shrub or other object. Clusters usually remain stationary for an hour to a few days, depending on weather and the time needed to find a new nest site by scouting bees. When a suitable location for the new colony, such as a hollow tree, is found the cluster breaks up and flies to it.
Honey bee swarms are not highly dangerous under most circumstances. Swarming honey bees feed prior to swarming, reducing their ability to sting. Further, bees away from the vicinity of their nest (offspring and food stores) are less defensive and are unlikely to sting unless provoked.
In most situations when a honey bee swarm is found on a tree, shrub or house you do not need to do anything. Swarms are temporary and the bees will move on if you patiently ignore them. Stay back and keep others away from the swarm, but feel free to admire and appreciate the bees from a safe distance.
Only if a serious health threat is present because of the location of the swarm, such as in a highly traveled public area, should you need to do anything with a cluster. An experienced beekeeper may be willing to gather the swarm and relocate it for you. Note that most beekeepers do not do this because they want the swarm; swarmers often have diseases and parasites that will be difficult to manage. Beekeepers that are willing to relocate swarms do so as a public service and may rightfully charge a fee.
As a last resort, you can spray a swarm of bees with soapy water or synthetic insecticide. Wait until after dark if possible. Soapy water sprays (up to 1 cup of liquid dishwashing detergent in a gallon of water) are preferred because the bees die peacefully; aerosol wasp and hornet sprays are more likely to irritate and agitate the bees before they die, increasing the chances of being stung. Spraying a honey bee swarm is a risky operation because of the large number of bees.