Bees in nature don't have screened bottom boards anyway. Some bees build in free air, its true, but its very uncommon. Usually they build in a tree or other cavity that is even MORE prone to debris buildup. With our flat bottom boards the bees keep them clean just fine usually.
I have considered an experiment just to see what happens if I build a TBH without a bottom board but just build it with the two sides joining at the bottom and letting debris buildup on its own. Just to see what gets in there and what develops because of it.
Scot Mc Pherson<br />McPherson Family Honey Farms<br />Davenport, IA<br />BeeWiki: <a href=\"http://beewiki.linuxfromscratch.org\" target=\"_blank\">http://beewiki.linuxfromscratch.org</a> <br /><br />Pics:<br /> <a href=\"http://linuxfromscratch.org/~scot/pics/bees/\" target=\"_blank\">http://linuxfromscratch.org/~scot/pics/bees/</a>