Supersedure is the replacement of a queen without swarming taking place and probably relates to a diminution of her pheromone production. The queen's pheromones are what keeps the colony together as a single entity and allows all members of this superorganism to recognise their own colony.
Of all the pheromones used to control the communication and activity of the hive 'queen substance' is one of the most significant. The queen's major pheromones are now known to be two acids produced in the mandibular glands. These are 9-keto(E)-2-decenoic acid and 9-hydroxy-(e)2-decenoic acid (abbreviated to 9ODA and 9HDA for obvious reasons). Exposure to these pheromones suppresses both ovary development in the workers and their interest in rearing a new queen.
These pheromones are transmitted around the hive by the workers touching, licking and grooming the queen and subsequent food sharing and antennal contact between other workers so they are constantly aware when the queen is present in the hive. The rapid transmission of the queen's pheromones around the hive enables them to respond quickly if she is missing or if the quantity of pheromones becomes diluted because the queen is failing. The quantity of pheromones the queen produces depends on her age, whether or not she is mated, the time of day and the time of year. In queens more than about 18 months old the strength of their pheromones starts to reduce consequently starting the process of her replacement either by supersedure or swarming.
Older queens are more often superseded than young ones so it is likely that the immediate cause of supersedure is reduction of the pheromone production by the queen. A queen that has been injured is frequently superseded. Colony size also affects whether the queen is superseded with larger colonies more likely to supersede the queen than smaller ones. In a perfect supersedure the old queen will remain in the hive laying eggs until the new queen is mated and laying after which time she may either politely die or be killed by the workers. During an imperfect supersedure the queen may die or be lost at any point during the new queen's development. This has the disadvantage that, in the event of the new queen not being successfully mated and laying, eggs there will no chance for the workers to raise a new queen because of the absence of eggs.
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