For relatively new beekeepers, there is likely nothing more frustrating than coming up to check your hives, only to find that half of them have vacated the hive entirely. Fortunately, this is not a case of colony collapse disorder, which results in all of a hive’s worker bees suddenly disappearing.
More than likely, the missing half of the hive is nearby, and all it takes is calling a few fellow beekeepers in the form of swarm chasers. “A swarm is the division of the honeybee colony into two parts,” according to Donald Lewis, an entomologist and Iowa State University professor. “One part of the colony will stay where they’ll continue to grow, reproduce, and make honey. The swarm leaves the colony in search of a place to set up elsewhere.”
As to why swarming occurs, it’s typically due to overcrowding within a hive or possibly due to genetics, per Lewis, who said, “There is a predisposition in some bee strains that makes it more likely for them to do that.” It may even be a simple matter of an older queen getting pushed out by the new one. “The old queen would go with the swarm, taking half the existing colony and all the honey they can carry when they depart,” says Lewis. “A swarm generally flies a short distance and then hangs out on tree limbs, stop signs, the side of a house, or perhaps in a playground.”
The chances a swarm has of becoming a thriving wild honeybee colony depends largely on where they settle. “If the swarm cannot get inside a protected location, they’re not likely to make it through the winter,” Lewis said.
As to how beekeepers can avoid losing half their hives to swarming, they can divide them before it happens, recapture the swarm afterward and give it a new hive, or buy a bee type known for their low swarming tendencies. For beekeepers or even regular, non-beekeeping folks who spot wayward swarms, it might be best to find some swarm chasers willing to gather the bees up safely.
Dan Maxwell, a Freeland, Washington beekeeper, says he’s often responding to calls for help removing swarms, but, by his own account, “[he] only work[s] with honeybees.” For swarms on tree branches, Maxwell only needs a vacuum with adjustable suction that won’t harm either the worker bees or the queen. Unless they’re otherwise provoked, honeybees seldom sting whenever they’re swarming. “Swarms are usually not in the stinging mood because they have gorged themselves on honey to start the new hive,” Maxwell said.
For those who run into swarms when the weather warms up, do not panic, spray insecticide, or throw rocks at them, because, per Lewis, “These are beneficial insects. You don’t have to needlessly kill them. Simply give them a wide berth, and chances are, they’ll be gone in a day or two.”