Barcoded Bumblebees Explain How Jobs Change Inside the Hive
In a beehive, everyone has a job. It’s like The Giver, only bumblebees can see in color. The employee hierarchy of the hive isn’t as clear-cut from the outside, though, which is why scientists who wrote about the bees in a study published Tuesday had to painstakingly equip bees with tiny computerized backpacks in order to learn more about the hive mind.
Writing in Nature Communications, a team of biologists and engineers explain how they used a tagged tracking system to track the movements of bees with different jobs. In particular, they wanted to determine which class of worker bees was most likely to replace forager bees when the hive is disrupted.
While all bees are born genetically identical, epigenetic changes that modify each bee’s DNA after birth help decide the job they’ll do in the hive — whether searching for food as a forager or doing hive chores as a worker. Queens are always exempt from work, but the members of the hive’s laborious lower class can sometimes switch jobs. The factors that drive worker bees to take on these new roles aren’t well understood, but tracking the bees with their backpacks shed some light on the hive’s organizational flow chart.
Between July and October 2015, the researchers followed approximately 1,700 individual bees living in 19 semi-natural colonies in Bedford, Massachusetts. Using barcode-equipped “BEEtags” stuck to the insects, the scientists traced millions of nest behavior sequences and thousands of foraging transits. When the researchers messed with the flow of forager bees, these data revealed the ways in which hives adapt to survive in superorganism harmony.
“Division of colony labor among workers is widely considered the key adaptation of social insects, with the specialization of workers on specific tasks, theorized to improve colony performance,” the study authors write. “However, individual workers generally show flexibility in task performance and social insect colonies are able to reallocate workers to different tasks when colony demands change.”
Here, when the scientists removed forager bees from their hive, they determined that the bees with the highest probability of switching to foraging were the ones that were already centrally located in the hive. These bees had the most interaction with the food storage area, which “suggests that these individuals were most aware of the resource needs of the hive,” the scientists explain in an accompanying statement released Tuesday.
These bees learn they must change their role in the hive by picking up on general social signals, signals stored in food pots, and hunger signals from larvae, the authors explain. Ultimately, it’s a worker bee’s spatial occupancy in the nest that predicts whether or not it must become a forager when the time comes to step up. In this case, those who are at the center of the hive are always next in line.
This study is in line with previous genetic research that determined that the methylation patterns in worker bee DNA — another example of epigenetic change — shift when their jobs shift, confirming that for bees, switching jobs is literally a life-changing step. It also supports the idea that hives thrive because of the inherent flexibility within the colony. Shifting labor demands isn’t just a quirk of bee culture but a system for transferring individual purpose that weighs the scales towards success.