Running screened bottom boards sitting on old pallets and have found that the bees are chewing up the comb in the bottom box. Just a little pollen stored there and no brood. is it possible they are getting too much ventilation?
I don't think it is a problem of too much ventilation. I think it more an act of dearth. I have found, if you have undrawn frames in a hive during a dearth, the bees will just chew those frames and put holes all through it. If the frames are drawn foundation it may be just some hygenics or house cleaning at work.
I've had some problems forom time to time with ants chewing up comb on the lower parts of the frames with screened bottom boards. They don't take a lot but can evade the bees because of the screen. I have a swarm trap set up not to far from my hives and the ants are havign a lot of fun with that!