"The Swarm" isn't just the name of a horror movie from the 1970s, it's also what you see when beehives become overcrowded and half the colony buzzes off.
About 8,000 honeybees now call the Plum Creek Nature Center's demonstration hive home. But that's a lot of bees to pack into one place, said beekeeper Mike Rusnak, who hosts "Meet a Beekeeper" programs at the nature center's bee exhibit.
"The primary reason honeybees swarm is overcrowding," he explained. "There are too many bees in their confined space."
During a swarm, the queen bee will take about 50 percent of the adult bee population with her to find a new home. By this time, a new queen is waiting in the wings at the original hive.
"The swarm usually takes place a day or two before the new queen emerges," Rusnak said. "The swarm that leaves will go to a nearby surface – a branch, a building, etc. – and wait for scout bees to return to the swarm with information on a potential new hive location."
The swarming bees are so excited, they will do a "waggle" dance – similar to the dance that indicates a food source has been located – to announce a new homestead location has been discovered.
"Other bees, after inspecting this new location, will return to the swarm and communicate their approval," Rusnak said.
Once bee colony members agree the new site is satisfactory, the swarm will leave the temporary resting spot and head for the new hive.
At Plum Creek, the swarm left the demonstration hive, which is visible from inside the nature center, and returned, only to leave again, which sometimes happens, Rusnak said.
"It's somewhat unusual for the swarm to return to the hive, but not unheard of," he said.
Rusnak stressed that the swarming phenomenon is not seasonal, it's more about hive occupancy levels. But he also noted that a beehive that has a strong winter will usually swarm in May or June. The bees that buzz off can't wait too long to swarm. If they do, they might not have enough time to store enough food to survive winter, he added.
"As the beekeeper saying goes, 'A swarm in May is worth a bale of hay; a swarm in June is worth a silver spoon; a swarm in July ain't worth a fly – because it's gonna die."
According to the University of Illinois Extension, if you see a swarming bee colony resting on a branch, building or other structure as it awaits news about a new home, don't be alarmed.
"Honeybees in swarms are usually docile and those with colonies in trees rarely attack, unless provoked," according to the agency.
If the swarm doesn't leave after a week or so, call a professional beekeeper to move it for you so these beneficial pollinators aren't harmed.
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