Bees swarm in the spring as a way of reproducing the hive. The hive literally splits in half and the old queen leaves with about half the work force - mostly young bees. The bees who have been getting ready to swarm for weeks, have their stomachs full of honey and are ready to relocate.
The swarm pours out of the hive in a cloud of what looks like millions of bees but in reality is probably may be about 30,000 bees. The queen lands somewhere and the bees gather around her, clinging to each other in a large cluster. Generally the cluster is hanging from something - a branch, a fence, a gutter, although if the queen doesn't fly well, the cluster may form on the ground.
If you see a swarm in your locality - around your house, in your yard, in your neighbor's yard, CALL A BEEKEEPER before you do anything to destroy the bees.
Most beekeepers will not collect bees that have been sprayed with insecticide.
A beekeeper can come collect the swarm and put it in a new, good home. Killing the bees only causes a release of unnecessary poison into the environment.
Bees in a swarm are not prone to sting.
Their purpose at that time is to find a new home, not to attack you. Also their bellies are full of honey, making it much harder to sting.
Generally a swarm hangs in its location only a few days while scout bees go out and find new possibilities for homes - hollow trees, bee boxes, etc. The bees literally vote on which place seems the best to them and when a democratic decision has been reached, the swarm leaves and moves into the new place.
So even if you don't call anyone, the bees will leave in a few days. But do call a beekeeper and give the bees an immediate good home.
Things you need to determine when you call a beekeeper for help:
1. Are these honey bees? Yellow jackets look like this. You can see that they are mostly black and yellow. Honey bees look like this - they are more brown and orange.
2. How big is the cluster? Is it the size of a baseball? A football? A basketball?
3. What is the swarm hanging from? (a tree limb, a gutter?)
4. How high up is the swarm?
5. When did you first notice the bees?
6. Have you called anyone else to come?
7. Have you done anything to harm the bees? (sprayed them with poison, etc.)
8. Can you send a picture of the swarm from your phone or camera?
Then call a beekeeper - if you are in the Atlanta area, call me:
What a swarm may look like:
(also search "swarm" on this blog and you'll find other examples)
This swarm was on a shrub and could be collected from the ground. Here's the slide show of collecting this swarm.
This swarm in the second photo was high in the tree and required a ladder and a swarm catcher.
Here's a swarm on a shrub.
Here's a swarm on a fence.