Screened Bottom Boards as trampoline Extensive long term studies at Cornell University have demonstrated that screened bottom boards do not reduce mite build up in colonies. I think they are a waste of money. The mites that fall through them most likely are old and about to die anyway. However, if the bees use them as trampolines, well -- I guess they are entitled to a little bit of fun before we put them to work gathering honey for us!! -- Peter Borst <[log in to unmask]>