In a beehive, girls run the world. Led by the queen bee, her fellow females (called workers) perform every task from cleaning the hive to collecting nectar and pollen. The only time the outnumbered males (known as drones) are in the picture is to mate with the queen bee, after which they immediately die. But what factors determine a female bee’s placement in the hive hierarchy?
Conventional wisdom has suggested that differences in food quality are to blame. The “royal” jelly fed to prospective queens is thought to be of better quality than the “worker” jelly given to other larvae, causing the greater size and reproductive ability that distinguishes a queen from the rest. Yet research in the area has been unable to identify a single substance responsible for the developmental switch.
In pursuit of a different explanation, researchers from North Dakota State University and the US Department of Agriculture have looked at another variable in the larval diets of honey bees: the quantity of food. To do so, larvae were reared in 72 dietary groups. Each of the nine royal jelly qualities chosen (that contained different quantities of protein and carbohydrate) were distributed in eight varying amounts to the honeybee larvae after their 5th day of development. A further reference group, which received medium quality jelly, were allowed to feed as they pleased (ad libitum). Their queenliness was then assessed, using traits such as weight, head width, and lower jaw length.
As the team described in their paper published in Proceedings of the Royal Society B: Biological Sciences, “larger quantities of diet increased the queenliness of adults regardless of diet quality.” Even on a medium quality diet, all of the ad libitum bees became queens, and 58 percent of those on the highest quantity diet were also of queen status. Regardless of quality, no honeybees raised on the lowest quantity diet became a queen.
"For a long time people have thought that royal jelly contains a special substance that makes a bee a queen," corresponding author Dr Julia Bowsher from North Dakota State University told IFLScience, "but we found that it is only the amount of food."
The authors supported this conclusion with observations from the hive. “Nurse bees provide queen larvae with more food than workers throughout development,” they wrote in the paper. “When emergency queen rearing is necessary, nurses increase worker-destined larvae cell size in order to rear queens. Increased cell size likely allows nurse bees to increase provisioning for queen rearing.”
Having pinpointed the determining factor of what makes a queen bee, the researchers hope their results can help to address the worldwide decline in honey bee colonies.
"Beekeepers are concerned that the quality of queens has been decreasing, and many replace their queens every year," Bowsher explained. "By better understanding the conditions for raising high-quality queens, we can increase the resiliency of commercial beekeeping industry."