All this is further explained here. Similarly one may ask, do you need to use a queen excluder?
The usual purpose of a queen excluder is to keep the queen from laying eggs in the honey supers. Until your bees draw out most of the frames in the brood boxes, you have no use for honey supers and, therefore, no use for a queen excluder. So before using an excluder, always make sure it is in good shape.
Secondly, do commercial beekeepers use queen excluders? A backyard beekeeper with a couple hives in the backyard may want to use excluders to make finding the queen easier but a commercial beekeeper who works almost solely in pollination rather than honey production may not want the hassle and expense of excluders.
Correspondingly, how does a queen excluder work?
The idea behind a queen excluder is that the worker bees can easily pass through the wire mesh, and the queens cannot. They also exclude the drones. Beekeepers place excluders above the brood box to keep the queen from laying eggs in the honey supers.
Will a queen excluder prevent swarming?
Just like a queen excluder, the swarm guard keeps both queens and drones from passing through because the wires are close together. Worker bees are small enough to pass through easily. A swarm guard will prevent swarming for a time, but the presence of the guard won't stop the swarm impulse.
