Inside a hive, all females are the same when they are larval bees. Then, one female is selected as the queen bee, and she is fed a special diet of royal bee jelly. The jelly nurtures her into becoming the queen bee. The other females get a non-royal diet. Royal bee jelly is made by worker bees, for the sole purpose of developing a queen. As a result, adult queens are larger than the other bees, live longer and are the only fertile ones in the hive.

The reason is that a queen's stem cells can self-renew, but worker bees can