Hi Allen

OMF or screened bottom boards have been used by some in the UK for many
years.
I was by no means the first to use them locally and I have now had them in
continuous use for 22 years.

6 mesh may be cheaper but we would have trouble with wasps and possibly
robber bees that were on the small side.

Whilst I have experiance of upper and alternative entrances, they are rarely
used in UK. In particular when we use OMFs we use solid, insulated roofs
with no ventilation at all, other than the mesh at the bottom and a 100
mm-120 mm entrance about 9 mm tall.

Debris on screens...

No wax is built apart from the odd vertical stool, but even that is rare.
I have had some propolising of mesh but my findings are different to most...
I put this down to the space above the mesh up to the bottom bars of the
brood frames (which is 9 mm in my case).

Dead bees dry up on the mesh and are easily disposed of, even in the depths
of winter, if you have and entrance at the mesh level. I have no experiance
of brood chambers totally covered by mesh on the bottom surface.

Spring build up is initially delayed but when it does happen, it occurs at a
faster rate so that colonies on OMF overtake those on solid floors.

The bees recognise the space below the mesh as "outside", it is quite common
to see a worker "post" a piece of debris through an aperture.

Using OMFs makes the colonies more vulnerable if they are inadvertantly
placed in a frost pocket, not from the pont of view of temperature, but damp
and possible excess CO2 in the still air in the depression.


Regards From:- Dave Cushman, G8MZY
Beekeeping and Bee Breeding, http://website.lineone.net/~dave.cushman
IBList Archives, http://website.lineone.net/~d.cushman