I am often told that one of the things to look for before doing things like splits or installing Queen excluders is to have two full brood boxes. I have always wondered what exactly that term means. In a meeting last night I was told that it is more appropriate to say "two full boxes of bees".

My question is that since bees come and go depending on time of day and weather, how many frames of brood are required to meet the "two full brood boxes" criteria? I know a worker needs 21 days from the time the egg is layed to when she leave the brood cell so maybe the question is also ask as "how many frames does a great, good or inferior Queen lay in 21 days"?