I'm experimenting with the screened bottoms this year for the first time. I
built pallets that hold four hives each and the only bottom is 1/4 inch
hardware cloth. I reduced the entrance to avoid robbing with the hives so
close together. I'm in central GA and it is very hot and humid here today
and the hives that don't have screened bottoms have large numbers of bees
loafing around the entrances late in the evening. The hives on pallets don't
have any loafing outside. I'm not sure how this will work in the winter but
right now I like it and it seems the bees do also. One drawback I did see
today was that I was losing a little pollen from the bees walking across the
hardware cloth. A fellow beekeeper that told me about screened pallets, said
to place a small ramp inside the entrance(3/4 x 3/4 piece of wood cut on a
45 degree angle) so when the bees enter they run up the ramp to the bottom
of the frames, thus reducing the running across the hardware cloth floor. I
have some pictures of the hives if anyone is interested in seeing.