Researchers discover what causes honeybees to prepare for reproduction
When a colony of honeybees reaches the first stage in its reproductive cycle it builds a special type of comb used for rearing male reproductive bees, called drones. But what triggers that first stage?
A team of experts from the Department of Neurobiology and Behaviour at Cornell University, led by Michael Smith, set out to answer that question, reports the journal Naturwissenschaften – The Science of Nature.
Reproduction isn’t always a honeybee colony’s top priority. Early in a colony’s development, its primary focus is on survival and growth.
However, when the colony reaches a certain stage, its workers start investing in reproduction. The first step is building cells of drone comb, the special comb made up of large cells in which the drones are reared.
Drones develop from unfertilised eggs. Their sole purpose in a colony is to mate with virgin queens from other colonies, thereby spreading the genes of the colony that produced the successful drones.
Virgin queens in turn need to mate with drones before they can lay fertilised eggs that will become worker bees.
Queens will mate with over a dozen drones during their single nuptial flight, after which they are stocked with sperm for life.
Smith and his team were puzzled about precisely which colony features kick-start this key process of drone comb building.
Is it the number of workers in the colony? Is it the total area of worker comb? Or is it the number of brood in the colony? Or the size of the colony’s honey stores?
The Cornell University researchers found that while every colony built worker comb (non-reproductive comb), not every colony built drone comb (reproductive comb).
They discovered that an increase in the number of workers stimulated them to start constructing drone comb. This was seen whenever colonies contained 4,000 or more worker bees.
The researchers are still left wondering about precisely how an individual worker bee ‘knows’ how many other workers there are in its colony.
They speculate that this might have to do with how crowded individuals feel while working side-by-side in the hive. Further research is currently being conducted to shed more light on this mystery.
“Colonies with more workers built a greater proportion of drone comb, whereas colonies with more comb, more brood, or more honey stores, did not do so,” Smith said. “We estimate that a colony needs approximately 4,000 workers to invest in building drone comb.”
The researchers believe that their findings are also relevant to other social systems in which a group’s members must adjust their behaviour in relationship to the group’s size.