I'm going to be making a couple of swarm traps this winter. Essentially, they'll be five frame deep nucs with a board on the back to facilitate hanging in a tree. There are lots of youtube videos on making or using them. Almost every one starts with a comment about swarm scouts look for the ideal space, 40 liters, etc. A five frame nuc isn't 40 liters? Maybe the old comb, newer drawn comb and LGO persuade them to accept this smaller space?
It's like a mantra that swarm scounts look for 40 liters, however, I know of no one who hoists a full ten frame deep into a tree? The smaller ones work well.
I guess my question is, where back in the history of keeping bees did this originate?