If you are curious about bees, you may wonder why and how they swarm. In my opinion, this is one of the most fascinating aspects of bee biology. Swarming is their way of managing the size of their hive, and furthering their species. When a hive becomes too crowded they will do what we call, "throwing out a swarm." The old queen will leave the hive with the swarm, and new queen cells will eventually give birth to a new queen (they will fight it out to determine who gets to be the big mama in charge). The bees will often cluster on the outside of their hive on the day they will swarm, and this usually happens after several rainy days (we've had our share lately, haven't we?).
When it is time to go, the bees will start to fly in a frenzy, making an intense buzzing sound that is so much fun to hear and witness. They will sometimes hover for a while, but usually will slowly move towards the direction they plan to go. Sometimes they don't go much further than 10-20 feet away, such as this hive has done. They will then cluster on a branch, fence post, side of a house, etc., until the "scout bees" have found a nice place for the hive to make a home. The queen will be hanging at the center of a swarm, with all the other bees clinging to each other around her. There is no comb, beeswax, or honey in a swarm, so the bees are usually docile because they have no home or property to protect.
If you see a swarm, you should try to contact your local extension agent, or do a google search for your local bee club. Beekeepers such as us are more than happy to come and take your swarm. We simply knock them down off the branch into a box, and later put them in one of our hives, with some drawn out comb with honey to entice them to stay. Sometimes we will even go as far as putting a frame of brood (baby bees) in, because the bees have a hard time leaving the babies. Yet sometimes, when a hive has it in their mind to swarm, they are even going to swarm out of the hive you provided... so it is never a sure-fire thing. Just today we had a swarm leave one of our hives after we caught it last night (leaving the brood and all). Bees are wild animals, no matter how much we try to domesticate them for our own use, they will do as they please. If you are local to our area, check out our Scioto Valley Beekeepers website to access a list of local beekeepers who are happy to help with swarms. In Columbus, the Central Ohio Beekeepers have a similar program.