Queen Succession in Honeybees

http://www.alleghenyfront.org/img/contrib/honeybee.jpg (Oct. 9, 2007)

Adaptive Value

Where does Adaptive Value start and Phylogeny end?

To understand the adaptive value of behaviors such as a eusocial structure and queen competition, one frequently looks at the benefits these behaviors provided for a common ancestor.  It is therefore difficult to study one without an understanding of the other. 


Specialization: the benefits of becoming adapted to perform specific tasks

The switch from living individually to living in a colony led to many adaptive changes.  In a eusocial colony, the individual worker bees loose their ability to reproduce in favor of the adaptive benefits of a specialized society.  In such a society, a queen can be best adapted at egg laying and the workers can become specialized in foraging or defense. The first two weeks of an average worker bee’s life are spent specializing in “household” duties such as cleaning and caring for the young.  The last four or so weeks are spent in the field gathering nectar and pollen (Hambleton, 1934)

Interestingly, it has also been shown that the queen has specialized in roles beyond egg laying.  It is her duty to guide returning foragers carrying pollen to empty cells.  She does this by either meeting the returning forager at the entrance and guiding her to an empty cell or by sitting beneath the cell she wishes filled.  In experiments where the queen was removed, the worker bees spent several minutes looking for the queen and frequently ended up depositing the pollen in the burrow rather than locating an empty cell on their own (Breed and Gamboa, 1977).  In addition, the queen was shown to motivate the worker bees to work harder.  In hives where the queen had been removed, the workers showed a decrease in general activity within 30 minutes of her disappearance (Breed and Gamboa, 1977).    


Queen Competition

As discussed in Ontogeny, there are frequently a few prospective queens within a hive at any given time.  However, it is to a queen’s evolutionary advantage to only have her genes passed on to her progeny above those of her sister’s.  This leads to her killing other potential queens by cutting a small hole in the side-wall of a cell containing a developing queen and stinging the occupant (Tofilski, 2003).  The benefits of a eusocial structure are most pronounced when there is only one queen.  Therefore having worker bees allow a queen to kill other potential queens is an adaptive response for the colony.  However, there are times when workers must protect potential queens.


 Queen Succession during Swarming

The worker bees generally allow queens to kill other potential queens except when the colony is getting ready to swarm.  During swarming, 5000 to 50,000 workers, zero to a few thousand drones, and one queen leave the hive to start a new colony (Morse, 1963).  For this event to take place, a new queen must be raised to maturity within the same hive as the original queen.  The worker bees protect the new queen while they care for her.


Emergency Queen Rearing

All brood are initially fed a pheromone rich food called royal jelly.  After two days, the future worker bees are taken off this diet while the future queens maintain the same diet (Evans and Wheeler, 1999).  However, should a hive lose its queen, one of the developing worker bees is selected to receive royal jelly and become the replacement queen.  Selecting a brood less than two days old would ensure that there is no difference between the emergency queen and a typical queen.  Choosing an older larvae decrease the time the hive spends without a queen, but maximum efficency of the new queen is not guaranteed.  By removing queens at different times, it was shown that the hive selects emergency queens that are on average 3.4 days old at time of dequeening (Torilski, 2003).


Artificial Emergency Queen Acceptance

For a beekeeper to start up a hive, all that is needed is a queen of a desired strain with enough worker bees to care for the queen. The worker bees do not need to be related to the queen.  In this case, the worker bees accept a non-related queen in order to survive as a colony.  Typically the queen is initially kept in a small box with mesh sides for a short amount of time so that the worker bees have time to acclimate to the new queen before they have to interact with her physically.