I have been interested in swarm prevention methods using specialized between the frame devices.
In 1897 Lewis Agustus Aspinwall patented a method of making bees feel like they had adequate room so they would focus their attention on honey production instead of swarming. Aspinwall’s principle encouraged the bees to expand their hive upward into the empty honey supers that were place on top of the hive.
The following quote is taken from Aspinwall’s 1908 patent # 891.584:> In my present hive I employ similar brood or comb frames, and I prefer to arrange the same alternately with dummy frames that are filled in with a series of similar or parallel strips or slats. These slats may be placed in any desired direction and so close to one another as to leave between them about a bee-space, and the slats are preferably as wide as the dummy frames, and they are so close as to prevent the bees building comb in the frames, but yet at the same time allowing room for the bees to travel through the dummy frames from one comb frame to the next and in this way providing ample room for all the bees and for the increase of the bees, so as to overcome the tendency of the bees to swarm at certain periods.
I have been experimenting with some modifications to the Aspinwall method - the reasoning makes sense - but I can’t confirm yet how well it prevents swarming. I haven’t heard of a single swarm in our area this year - probably due to the drought.