I know the answer is here somewhere - just having difficulty locating.
I have heard/seen that by forcing the bees to enter the hive thru a particular screen size (#4?) helps the guard bees to better defend, and that the robbers are reluctant to enter. This is NOT an entrance reducer, per se, in that the entire entrance is open - just covered with this screen large enough to let one bee pass thru each screen hole.
Is #4 the right size, and does this method seem to help?
EAS Georgia Certified. "Tradition - Even if you have done it the same way for years doesn't mean that it is not stupid."