The only sure defense against bees and wasps is to deny them access to the nectar. I’ve had really good luck with the WBU saucer feeders.
Before I had those feeders however I would swab the ports of my old feeders with almond or cherry extract (purchased at any grocery store baking isle), the bees will avoid that scent. This really works but it wears off fast and you have to reapply the extract every day.
Another trick you might try is to use a super-concentrated sugar water mix (two parts water, one part sugar), and pour it into a shallow plate, preferably a big yellow one (bees seem to be attracted to that color). After all the sugar water is gone, the bees should be gone too.
Or Hummingbirds.net recommends: “reducing the sugar concentration to 1 part sugar in 5 parts water will make it less attractive to insects, but probably won't make the hummingbirds lose interest.”
Wild Birds Unlimited saucer style feeders are also good at preventing ants. They all have a built-in ant moat that you fill with water to stop the ants. Our stores also have ant moats you can add to any feeder. Simply fill the little container with water and hang your feeder below. Once again the ants can't cross the water moat to reach your hummingbird feeders' nectar.
Do you have a bird question? I answer lots of bird and nature questions at http://lansingwbu.blogspot.com/ Or you can email me at firstname.lastname@example.org.