Dee and All If I can respectfully suggest, your proposed experiment will do nothing to clarify in the mind of sceptics whether or not 4.9 is useful in controlling Varroa. The experiment Allen suggested is crucial to convincing others that 4.9 is a useful addition to IPM for Varroa, but if there is no *direct* evidence people will be slow to take it up. Why will your experiment fail to make anything clearer? It is obvious to everyone that drone brood is a better home for Varroa than any size of worker brood. But the success you claim for 4.9 is not, I assume, because small bees stop making drones?! Much more likely would be that the small cell size inhibits the mating of the mite in a cramped cell, or that the small cells somehow awaken unusual hygienic behaviours as some have reported. What is really needed? Moving some of your resistant bees from 4.9 back to larger sizes in a way that preserves the normal ratio of workers and drones, in colonies that start with similar mite loads, and following through at least one season the performance of those colonies. Maybe Bee-L participants have a better idea of how to do this that I have, remembering that you need everything except comb size as equal as possible. If you shake an entire 4.9 colony into 5.4 comb will it adopt 5.4 worker cells as worker and '5.4' drone cells as drone? Why is this needed? You are making big claims for 4.9 and it is possible that this is one of the best ways to move to sustainable beekeeping. It is also possible that 4.9 is largely irrelevant and that other factors give you the resistance to the mite. At the risk of repeating old arguments, the process of allowing a crash in numbers of colonies due to Varroa and then breeding from survivors must mean that your bees are now inherently more resistant to Varroa. What is not clear is the relative contribution of genetics and 4.9 - and only those beekeepers making progress with 4.9 can perform those experiments and tell us the answer! all the best Gavin.