A recent study conducted in Nepal and published in Apidologie assessed the optimal size of cell cups for both rearing queen bees and producing royal jelly.Researchers compared cell cups with different diameters (6, 7, 8, 9, 10, 11, and 12 mm), all with the same height (10 mm). They measured graft acceptance, royal jelly yield, and queen size.The results showed that 9 mm was the optimal size for graft acceptance and queen performance, while 10 mm was best for royal jelly production.

Go to the scientific paper here.