In the Puget Sound region on the West Coast of Washington, many of the
hobbiest beekeepers use these boards.  I have never seen them used in MT,
Idaho, Wyoming, or eastern WA.
 
These beekeepers also often paint their hives dark colors.  They argue
that the cool, rainy weather, intermixed with sunny days tends build up
humidity and condensation in the hive, especially in the spring.  They
also report, and I have seen, water running out of the hive and dripping
off the front edge of the bottom board - even when there has not been any
rain.
 
The dark colors are supposed to increase the internal hive temperature -
the old black box theory.
 
The slatted bottom board presumably increases ventilation and gets the
brood chamber up off the wet bottom board.  I have noticed that incomiing
bees often avoid the wet floor, going right to the slats.
 
All of this is supposed to reduce chalk brood, other fungal problems,
etc.  My impression is that there is some validity to this.  If nothing
else, you probably get better air-flow across the bottom board which
should help dry it out.
 
Bees in boxes with slatted bottom inserts seem look a bit better.
 
James Bach, WA Dept. of Agriculture has inspected thousands of hives in
WA.  He would be a good source of information concerning whether this
really works.
 
Jerry Bromenshenk
The University of MT
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