If the bees don't have the correct odor of that particular hive they are expelled. The new virgin queens produce a special odor called a sex pheromone to attract drones during the mating flight .
Bees also use odors to help locate their hive, or their new home after swarming.
To humans this pheromone smells lemony. When a bee stings, she releases an odor called an alarm pheromone to alert others to the danger. This alarm pheromone smells like bananas and attracts other bees to come to the defense of the hive. The queen bee has her own pheromones in addition to the smell she produces when ready to mate. When a beekeeper wants to requeen a colony by introducing a queen from another source, he or she must place the queen in a cage within the colony for up to five days in order for the worker bees to get used to her odor.