Bees form a fragrant phone tree to transmit messages

PICTURE: A group of bees on the CU Boulder campus. view more

Credit: Peleg Lab

The honey bees are playing an odor-guided telephone game to lead members of the colony back to their queen, according to a new study conducted by the University of Colorado Boulder. The research, published today in Proceedings of the National Academy of Sciences, emphasizes how insects with limited cognitive abilities can achieve complex feats when working together – even creating something that looks like a miniature and buzzing version of a telecommunications network.

The findings also serve as proof of the bee’s love for its queen. These matriarchs are the most important members of any hive: They are the only females that can reproduce. The queens, like other members of the colony, can also communicate using pheromones or small and fragrant molecules that bees produce through special glands.

“It’s very important for bees to know where the queen is and to stay close to her,” said study author Orit Peleg, an assistant professor at the BioFrontiers Institute and the Department of Computer Science at CU Boulder.

Pheromones, which are too small for scientists to observe directly, can travel so far before dispersing into the air.

This is how bees become creative in transmitting messages. Relying on experiments with live bees and computer simulations, or models, Peleg and her colleagues discovered that when the queen starts sending pheromones, nearby insects take note. They stop what they are doing, start creating their own pheromones, and then transmit those scents to the friendly bees that are further away.

Peleg added that the results could one day help engineers design more efficient telecommunications networks – for humans.

“There are many examples of animals, like ants, laying pheromones in their environment,” Peleg said. “But these pheromones only passively diverge according to the laws of physics. Here the bees are actively directing that signal.”

Shake it

That conclusion, she added, came from a random observation. During a previous study, Peleg and her colleagues monitored how bees form giant swarms – or wavy spots composed of thousands to as many as 100,000 bees.

In the process, researchers noticed something strange. As bees in their experiments gathered around the queen to build a swarm, a large number of them began to engage in what scientists call “fragrant” behavior. They stuck their rear ends in the air and fluttered their wings furiously.

“When they inflate their wings, they draw air over their pheromone glands, blowing out those molecules,” Peleg said.

She and her team wanted to know what was behind this version of insect twerking.

To do this, the group set up a video camera in the arena and filmed the bees in the process of swarm formation. The researchers then analyzed those images using machine learning tools that automatically tracked the locations and orientation of the bees in the colony.

The team found that the bees did not seem to spread their scent by accident.

“The signal is broadcast in a certain direction, and that direction is usually away from the queen,” Peleg said.

Calling home

Imagine a tree telephone insect: the bees closest to the queen catch the breath of its odor molecules and then smoke their own pheromones to the bees behind them. The next layer of bees in turn conveys the message and the chain continues until each bee in the colony enters the secret.

“It’s almost reminiscent of a telecommunications network where you have antennas that talk to each other and amplify the signal so it can reach further,” Peleg said.

Dieu My Nguyen, the lead author of the study, noted that at the height of this communication craze, the beehives of the hive were mostly evenly distributed throughout the arena.

“The distance between the bee smells was very even,” said Nguyen, a computer science graduate at CU Boulder. “This suggests that there is some sort of concentration threshold beyond which pheromones can be detected and that bees have responded to it.”

Peleg, Nguyen and their colleagues say there is still a lot they don’t know about how these communication networks work. Can only some bees, for example, transmit messages to the queen or can all members of the hive sniff and chatter when it suits them? For now, the team is happy to be able to get a new breath of social life from these curious insects.

“We got a few bee stings,” Nguyen said. “But it was true for those beautiful movies.”

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Other co-authors on the new research include CU Boulder graduate Michael Iuzzolino and student Aaron Mankel. Katarzyna Bozek from the University Hospital of Cologne and Greg Stephens from the Okinawa Institute of Technology and Vrije Universiteit Amsterdam also contributed to this research.

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