October 03, 2018
When moving as one, a honey bee swarm, which occurs after a hive has grown too large and must divide to survive, is basically a superorganism, changing shape whenever responding to strain or stress, even when doing so costs several individuals their lives. With a new queen at the center, this superorganism of a swarm will attach itself onto the bottom of a branch or similar spot, taking shape as an upside-down cone—all while worker bees scout for the right place to create a brand-new nest. Amazingly, this cone is able to handle rain and changes in temperature by adapting its appearance and shape. Even during strong winds, this cone can change by flattening itself and hugging the branch’s underside closer.
The ways in which a swarm moves as one has fascinated scientists for years, with several Harvard researchers opting to study this response recently through a formal study. To learn about honey bees’ swarming response, Orit Peleg as well as her colleagues manually attached a sizable bee cluster onto the bottom of a board in their lab before horizontally shaking the board in order to mimic high winds.
While the board was shaking, the bee swarm began to sway, just as with trees during high winds, and the cluster began to flatten against the board. The cone of bees was several tens of centimeters tall before the shaking, but it lost nearly half its height within 30 minutes, causing the swarm to be less vulnerable to swaying. Through video to track individual bees’ movements, Peleg’s team saw that honey bees at the cluster’s tip climbed upwards slowly toward the base, spreading out during the shakes and therefore clarifying why swarms flatten.
However, this wouldn’t explain the reason the bees knew to climb up once the shaking started. According to Peleg’s team, it’s not likely the bees were just climbing against gravity, as they would’ve had trouble detecting gravitational forces during a violent shaking similar to that of wind. The researchers also produced a model for simulating the physical sensations individual honey bees experience whenever the swarm shakes. They showed honey bees tolerate local physical strains while they cling together, and the honey bees at the cone’s base—next to the branch, board, or other surface the swarm has attached to—experience the most stress.
Per Peleg’s team, it’s possible it’s the physical strain the swarm feels that is the cue. Whenever individual honey bees experience physical strain, their response is to climb upwards—even if this means they’re moving toward the higher-stress area. Due to the climbing they perform, individual honey bees must shoulder the greater load, but they appear willing to do it for the benefit of the colony.
Photo By grafvision