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If it's a bad idea to hit a nest of hornets, it's definitely a bad idea to shake a swarm of bees. Unless, of course, it's for science.
A team of researchers from Harvard University spent months shaking and shaking swarms of thousands of bees to better understand how bees collectively collaborate to stabilize structures in the presence of external loads.
The research is published in Physics of nature.
"Our study shows how living systems exploit physics to solve complex problems at much larger scales than the individual," said L. Mahadevan, a professor of applied mathematics at Harvard's John A. Paulson School. SEAS), professor of organismic and evolutionary biology (EPO), professor of physics and lead author of the study. "We have demonstrated that bees can harness the physicality of the environment by solving a global mechanical stability problem using local detection and action"
This research follows earlier work by the group showing how bees can also collectively maintain the temperature of a cluster using local detection and actuation to avoid overheating or overcooling.
Bee swarms form when a queen bee goes out with a large group of worker bees to form a new colony. While scouts are looking for a new nesting place, the colony forms a living and breathing structure, consisting of their own bodies, on a nearby tree branch. These clusters maintain their structure and stability for days in the presence of wind, rain and other external loads.
"The main question of our research was that, since individual bees can probably only detect their interactions with their neighbors, how do they make changes to maintain the overall structure of the cluster?" said Orit Peleg, a former postdoctoral fellow at SEAS and co-first author of the paper.
Peleg is now an Assistant Professor of Computer Science at the University of Colorado – Boulder.
The researchers built a swarm of bees by tying a queen to a mobile board and waiting for the bees to gather around her. Once the cluster formed, the researchers simulated the wind by shaking the board horizontally and vertically.
They observed that the swarm begins with a cone-shaped structure, with a certain height and a base area. When they are shaken horizontally, the bees create a flatter cone by decreasing the height and increasing the base area. When the shakes stop, they return to their original shape.
Bees know how to move because they react to local changes in their neighbors.
"Individual bees can indicate the direction of tension based on their relationship with their neighbors," said Jacob Peters, who recently defended his doctorate at the CEO and co-authored the document. "Because the strains on the swarm are the highest at the top of the swarm, where they are connected to the branch – or in this case, on the board – they know how to go up. are influenced by this gradient, so it leads to a coordinated movement. "
Imagine playing ring-a-round-the-rosy blindfolded. You do not know which direction everyone in the circle moves, but you know your neighbor's direction because you hold his hand. You do not know when everyone falls, but you know when to fall because your neighbor falls. Like bees in a swarm, you follow the indications associated with your neighbor's local strain.
When the cluster breaks in horizontal agitation, the distribution of the load by individual bees increases, but the colony is generally more stable. The researchers were able to imitate this behavior in a computer simulation by imposing rules at the local level.
The researchers also found that when the bees were shaken vertically, the cluster did not adapt its shape because the local variations of the deformations were lower.
This research could have broader implications for how we think about control algorithms and collaborative machines.
"When we build machines or materials, we use simple control algorithms, from top to bottom, in which you have a centralized control that controls all moving parts of the machine," said Mr. Peters. . "But in this system bees realize this coordinated change of form without a central controller. Instead, they are like a set of distributed agents with their own controllers and they have to find a way to coordinate themselves without explicit long-term communication. By studying these types of systems, it could inspire new ways of thinking about distributed control of systems as opposed to traditional centralized control. "
This research was co-authored by Mary Salcedo, a graduate student of the CEO. It was funded by the National Science Foundation.
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