|A swarm in a holly tree|
People get SO freaked out at the idea of a swarm of bees. It brings to mind "killer bees" and seventies horror movies. But all it really means is that a beehive has reproduced- and people should be less afraid of these bees, not more, because the lack of honey to protect makes swarming bees incredibly docile. If you think of the hive as an entity (rather than the individual bees), it makes sense that the way a colony reproduces is to swarm. They do this a lot in the spring, mostly because, as the colony builds up its population, the hive can begin to feel cramped. The bees produce a new queen, and the old queen takes about 60% of the hive and flies off to find a new home. This leaves the new queen with plenty of room. The queen and her bees land on a branch or a wall or almost anything, really, and then they hang out while scout bees look for new digs.
|Wall cavity after bees are (mostly) removed|
Of course, more often, the bees are not collected by a beekeeper. They sometimes find a place to live that's ok, like a hollow space in a tree, but often they find a place that seems ok to them but is awfully inconvenient to people. Then they build a colony in a space like an attic or inside a wall, and you don't notice until one day you're mowing the lawn and wonder why all those bees are flying in and out of that little gap between your wall and the air conditioner.
|A frame full of brood comb|
However, a brave homeowner who helps out with the extraction will be amply rewarded, because a cutout is SO. COOL. It can go in a lot of different directions, based on where the bees are located and how they've built the colony, and how long it's been there, but the beekeeper will basically cut an opening and remove the comb (with various cutting tools) and the bees (with a modified vacuum. Yes, I'm being serious - a vacuum). The part of the comb with the brood (i.e. baby bees) is placed into frames and set into a deep (which is what the bottom box of a bee hive is called). We take that brood box home, and empty the vacuum contents onto it, and go from there. The homeowner can expect a fair number of lost bees wandering around over the next few days, but they dissipate over time, since they can't reform a colony without the queen and brood.
Beekeepers generally will not charge anything to come rescue a swarm, but a bee extraction requires specialized equipment and a LOT of work, so expect a charge (ask up front what it will be). Also, a bee swarm, by definition, has a queen, which is what makes it possible to establish that swarm as a colony. In an extraction, the queen bee may not be captured, or she may be killed or damaged, so the bees that the beekeeper takes home are not nearly the incentive that a swarm is. Still, do please call someone (you can google your local bee club or association for references) as soon as you notice the issue; colonies only get harder to remove the longer they stay. And since they can contain tens of thousands of bees, it's better to remove them to a safe place, even though honeybees are far more docile and less prone to sting than, say, wasps or yellow jackets. They will definitely still sting you if you're bothering the hive, and if that hive is in the wall of your garage, for example, then you run into a major conflict of interests.
All that being said, new colonies are fun fun fun for a beekeeper. It's often hard work, rescuing bees, but it's all worth it when you get the colony to thrive in a good home. Nothing makes me happier than relaxing on a sunny afternoon out in the bee yard, watching happy colonies of bees do their thing.
P.S. If you're in the metro Atlanta area, absolutely feel free to contact me for your swarm issues. I'm always happy to answer questions, and more bees= more colonies= more soap and lip balm.