Here is an interesting quote and observation about the ventilation holes in migratory lids from the Australian Beekeeping Guide, 2014, by Russell Goodman ad Peter Kaczynski.....page 68 and 69...one of these guys has 51 years experience with bees...
"There is some debate about the use of air vents in migratory
lids during winter. When the ventilator mesh is fixed to the
inside of the vent hole some colonies will seal the mesh with
propolis, thereby restricting ventilation. Other colonies will
choose not seal the mesh, but we don’t know the reason for
this choice. On the other hand, when the ventilator mesh is
fixed to the outside end of the vent hole, the bees don’t seal
So there you have it. Some colonies seal it and others don't, I wonder why? And then they all don't seal it if it is fixed to the outside. How interesting.