Bees and wasps commonly become attracted to hummingbird feeders due to the fact that a majority of feeders have plastic yellow flower attachments. Bees may even try to nest in humming bird feeder and constantly steal the nectar that you put in it. It's possible for the bees to fill up the feeder so much that the hummingbirds can't get into the feeder at all. Trying to swat at the bees and other pests can be ineffective and exhaustive, so it's best to troubleshoot your bee problem until it stops.
Remove any parts of your bird feeder that have the color yellow on them. If you can't remove the part, you should paint it red, which is a color that the bees will not be attracted to.
Purchase an attachable bee guard for your bird feeder or you can purchase a bird feeder that comes with a guard. Such feeders include Perky-Pet and Four Flowers (see Resources section). Make sure that the feeder or attachment that you purchase has a mechanism to stop dripping.
Move your new feeder at least two to three feet from where you previous feeder was. This will confuse the insects who expect the food source to be in the same area. The hummingbirds will easily be able to find the feeder.
Take the feeder down for one day if the bees are still getting into the feeder. It is possible that the bees will give up looking for the feeder within this time. However, the hummingbirds should have no problem finding it shortly after you put it back up again.
Reduce the amount of sugar concentration in your feeder until the bee problem stops completely. For example, you should have one part sugar mixed in five parts water to make the mixture less appealing to bees.