"Hygienic bees have a strong tendency to clean things up, removing pupae and larvae if they are dead or dying," said Ratnieks, who has been studying bees, ants and wasps for 25 years. "What this hygiene can do is control certain types of disease, particularly diseases of the brood like chalkbrood, American foulbrood and varroa mite. "In the case of varroa mites, the female lays eggs on the pupa in its cell. These eggs turn into baby mites. Hygienic bees can detect this is taking place and they remove the wax cap to the cell and yank out the pupa. So they don't actually kill the female varroa mite, but they do prevent her breeding. It is not a complete control against varroa, but it can slow down the growth, therefore helping beekeepers keep on top of the disease."