The honeybee queen serves as the reproductive center of the colony, a role that makes her existence paramount to the entire hive’s survival. Her presence dictates the behavior and physiology of thousands of worker bees through a complex system of chemical communication. Rejection of a queen, whether she is the resident mother or a newly introduced replacement, is a natural and dramatic mechanism the colony uses to ensure its genetic fitness and continuity. The decision to reject is not arbitrary but is rooted in the collective instinct to maintain a productive and healthy population.
Failure of Queen Pheromones and Health
The queen maintains her dominance and the colony’s social order primarily through the release of Queen Mandibular Pheromone (QMP). This complex blend of compounds, produced in her mandibular glands, is constantly circulated among the workers via grooming and feeding, acting as a chemical passport and a regulator. QMP’s main function is to suppress the development of worker bee ovaries, preventing them from laying eggs, and to inhibit the rearing of new queens, thereby stabilizing the hive.
A decline in QMP production is the first biological signal that a queen is failing. This drop can occur for several reasons, including natural decline due to old age or a lack of sperm reserves from initial mating. Physical damage, such as a crippled leg, or disease like Nosema, can also reduce the quality or quantity of her pheromones.
Worker bees detect this reduction in the chemical signal immediately, recognizing that the queen is no longer reproductively fit. The pheromone she distributes with her feet signals her movement and vigor; a reduction in this signal alerts the workers to her inadequacy. Once the signal fades, the suppression of worker ovary development begins to lift, and the colony prepares to take action.
Colony Instincts and Supersedure
When the colony detects a failing queen through her reduced pheromone output, its primary response is often a controlled process called supersedure. This is the hive’s way of proactively replacing an underperforming queen without undergoing the turmoil of swarming or a period of queenlessness. Unlike swarming, which is about reproduction and colony division, supersedure is purely a colony survival mechanism.
Supersedure is initiated when workers perceive a sustained dip in the queen’s egg-laying rate or a change in her overall health. The bees will construct only a small number of specialized queen cells, typically one to five, building them on the face of the comb within the main brood area. This contrasts with the many queen cells built on the bottom of the frames during a swarm preparation.
In a successful supersedure, the new virgin queen emerges, mates, and begins laying while the old queen may still be present and active. This period of having two laying queens ensures there is no break in the brood cycle, maintaining the colony’s strength. Eventually, the workers will favor the younger, more vigorous queen and stop caring for the older one, allowing the new queen to take over completely.
The colony may also reject a queen if it perceives a more immediate crisis, such as a complete lack of fertilized eggs. If the existing queen only lays drone eggs because she has run out of stored sperm, the workers recognize the failure to produce female worker bees, which are necessary for colony function. Furthermore, if the colony has been queenless for too long, worker bees may begin laying unfertilized eggs, a state known as laying workers, which often results in the immediate rejection and killing of any newly introduced queen.
Rejection of Introduced Queens
Rejection is most acute when a beekeeper intervenes and attempts to introduce a foreign queen to the hive. This immediate, aggressive response is driven by the colony’s unified scent identity, which is defined by the original queen’s pheromones. A new queen, regardless of her health, carries a distinct “foreign scent” and is instantly perceived as an intruder and a threat to the colony’s genetic integrity.
The most violent form of rejection is “balling,” where a large number of worker bees quickly surround the new queen in a tight, vibrating cluster. The workers use muscle contractions to generate intense heat, effectively overheating and “cooking” the foreign queen to death, or they may sting and bite her. This response is an instinctual defense mechanism to eliminate a perceived usurper.
Beekeepers mitigate this aggression by introducing the new queen inside a protective cage, which allows for a critical acclimation period, usually lasting between two and six days. During this time, the queen begins to acquire the colony’s specific hive odor, and her own pheromones slowly permeate the hive, helping the workers become familiar with her scent profile.
The worker bees will often chew through a candy plug in the cage, a process that naturally delays her release and ensures a gradual introduction. If the new queen is released before hostile behaviors like balling the cage have completely stopped, the workers are likely to kill her immediately upon contact.
Rejection rates remain high if the colony is not fully ready to accept a new mother. Workers often reject the introduced queen if:
- The scent of the previous queen lingers too strongly.
- The hive contains a developing virgin queen.
- The hive contains sealed queen cells.
- The new queen is released before hostile behaviors like balling the cage have completely stopped.