Did you know that bees swarm when when the queen bee leaves the colony with a large group of worker bees? It's how a new honey bee colony is formed. In the prime swarm, about 60% of the worker bees leave the original hive location with the old queen. This swarm can contain thousands to tens of thousands of bees. Usually, swarming takes place in spring, within a two- or three-week period, but occasional swarms can happen throughout the producing season as well.