If you discover a swarm of bees on your property please call a local beekeeper to remove them. An average swarm of bees can contain between 6,000-12,000 bees. Needless to say any insecticide spray will not be effective. Actually, the swarming bees are often very docile at this stage. By having a beekeeper remove these bees you are helping the environment by allowing another colony of nature's pollinators to go back to work pollinating crops and creating honey.