The standard explanation:

> When a queen begins to fail the colony recognizes this and initiates her replacement by rearing new queens in a process we call supersedure.  Little is known about the proximate cues leading to supersedure.  The current study examined the role of queen mandibular gland pheromone (QMP) and an unidentified “fecundity” signal from young brood as possible cues that could initiate the supersedure process. -- Pettis. 2006.  Proximate cues in the supersedure of honey bee, Apis mellifera, queens.

Again, the theories of supersedure fail to account for what we actually observe. The brood supposedly signals to the colony that everything is "all right." Except, when the colony is broodless, during the off season, they don't initiate supersedure. The way in which a queen maintains control over the colony is not adequately explained (yet). However, there may be a hint here:

> Cape honeybee workers have successfully invaded queenright A. m. scutellata colonies and simultaneously escaped reproductive suppression from the resident queen and brood. These “social parasites” rapidly develop into reproductives, lay acceptable eggs and mimic a series of queen pheromones. This pheromone mimicry by invading A. m. capensis workers causes a breakdown in reproductive regulation, resulting in reproductive anarchy. -- WOSSLER, 2002. Pheromone mimicry by Apis mellifera capensis, etc.

Using pheromones, the cape bee workers "impersonate" a queen, gain "control" of the colony, and wreck it. Sort of like an old queen who can't lay eggs worth a damn, but still has the colony "in thrall" and they fail to replace her in time. 

PLB

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