The job that a bee does in the hive depends on what it eats. A queen bee has a special diet. The workers build some large cells for the young queens, and start special treatment for them. They are fed on rich food, called royal jelly, produced by glands in the workers' heads. This allows them to develop into full queens. Only some bees are queens, because the adult queen in a hive makes a chemical that spreads round all the workers and stops them from becoming queens. If the queen gets weak, or the hive is very large, there is not enough of this chemical to work and it no longer has an effect.