This is natures way of increasing the honey bee population. When a colony be it in a bee keepers yard or a hollow tree in the woods starts to get to crowded the workers make queen cells several, many and a bunch. I don't for some reason a good queen cell picture.
Any how as the first of the new queens are hatching out of there cells the old queen and about half the bees in the colony take off. Queens have not flown for a long time so they get tired rather quickly and will land some place. Many of the other bees will surround her to keep her safe. They are not dangerous then either, as my grand daughter says. I have gotten them from Home Depot in town twice as the home office in Atlanta GA. has my name on record of a swarm remover. I am also listed on several places on the internet, fire department, police department, Animal control office, USDA office, county extension office and several pest control companies since in Michigan if you kill a swarm your breaking the law. Many ways of getting them in a hive. Some times if the swarm is at the right level you just set a hive under them and they march right in. Some times they are not to high up maybe 10 feet and it is clear so I have a bucket on a pole Do the snap thing that shakes them in the bucket and I pull the rope to close the lid then pour them in a hive. One was 35 feet up in a tree so I set my 10 ft step ladder in the back of a pick up and used a extendable paint pole with the clear suction hose and the bee vac to suck them out of the tree.
Swarms can take on many shapes and be in some crazy places.
this one was about 40 feet up in the tree could not reach it so used a 12 ga. shot gun to shoot the limb off the tree behind the swarm. the swarm fell as a they were and nearly hit the hive body I had set below then marched right in.
So if you see a swarm call a bee keeper to come get them. Do an internet search for a bee keeper in your area that collects them. Used to be till 2010 a bee keeper in Ohio that kept a list for all 50 states and some of Canada.