What is fed to a bee larva to turn it into a queen?

In a colony of honeybees, a fertilized egg can develop into a queen or a worker—depending on the diet provided to the developing bee. Early on, all bee larvae are fed a substance called royal jelly, which is a gelatinous substance produced in the head glands of ‘nurse’ bees. Royal jelly is composed of approximately two-thirds water, one-eighth proteins, 11 percent simple sugars, small quantities of Vitamin C, and various trace minerals and enzymes.

Source: Australian Academy of Sciences