For researchers at the University of Colorado Boulder, X-ray technology has offered a glimpse into a mysterious and elusive world: the inside of a honeybee swarm.
Although swarms can contain thousands of bees, the researchers found in a recent study that the transient clusters of insects are so mechanically stable and mathematically sound that they could provide clues into designing more resilient structures in the human world.
“The bees have a very — they almost have this intuitive understanding of the physics and the mechanics of that structure. And they respond to it,” said Orit Peleg, a senior author of the study and assistant professor of computer science at CU Boulder said. “It seems like bees are paying attention to mechanical forces.”
To examine how swarms are structured, Peleg and her team of researchers created a unique setup that enabled them to perform CT scans on swarms in a lab setting. They recreated swarms by attaching a caged queen bee to the underside of a rotating wooden disk and allowing worker bees to cluster around her. The researches then used an X-ray emitter and detector on either side of the cluster to gather images of the inside of the swarm.
During a swarm in nature, thousands of bees leave their hive along with their queen in search of a new home. Although it’s not always clear why bees swarm, it’s often triggered by overcrowding in the original hive. Once it’s left home, the swarm often takes refuge on a nearby tree branch or other structure while worker bees search for a location for a new hive. Meanwhile, the queen bee gives off pheromones that tell the worker bees to cluster together around her. They respond by layering on top of one another to create a dome-like mass with the queen at the center.
During this process, Peleg said, the bees have to assess what’s happening around them and decide how to arrange themselves for optimal stability.
“There isn’t a leader that is telling the bees what to do, although the queen is there,” Peleg said. “The bees are actually making their own decisions … based on the information they have at their nearby environment.”
In their study, Peleg and her team of researchers found that swarming bees arranged themselves in a way that distributed weight and mechanical force efficiently throughout the cluster. Each bee can support a maximum of about 35 other bees, but an even distribution of weight throughout a swarm cluster ensures that the bees don’t reach the limits of their strength. Additionally, the researchers discovered that swarms have the same basic structure at smaller and larger scales.
Part of the reason bees cluster in this way, Peleg said, is to help with regulating their temperature.
“It’s a little bit like huddling … people huddle and penguins huddle, and lots of other animals do that,” Peleg said. “If a single bee is more exposed to the environment, it can lose more heat. If it’s instead inside this big huddle, then effectively it has less surface area that is directly in contact with the environment.”
But bees in the cluster also hold onto each other to keep the colony intact. Although swarming is a natural part of bees’ reproductive cycle, it always comes with risk: if too many worker bees are lost or the queen dies, the colony is not likely to survive in its new home. According to the study, the mechanical stability of swarms can directly impact whether the bees will survive.
There is much to learn about the complexity of bee behavior, but the results of this study shed light on previously-unknown ways that bees cooperate with each other for their own survival.
“I think (bees) have this amazing, intuitive understanding of the environment and of physics and material science that we scientists are just starting to figure out,” Peleg said. “And I think we have a lot to learn from them.”