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When it comes time for honeybee swarm to split off from their mother colony and find a new place to live, something remarkable happens. To communicate most effectively, they organize themselves exactly like the neurons of a complex brain.
Sometimes, a honeybee colony grows too large, and so a swarm breaks off in order to find a possible new home, usually somewhere like a secure opening in a tree. Different bees check out different possible new homes, and those that have found a suitable landing site communicate this to the others by dancing, repeating a simple figure eight pattern that the other bees can interpret in order to know the direction and distance of their potential new home.
Time is of the essence here, since the entire swarm is exposed and vulnerable to the elements, and they’re also missing out on crucial honey harvesting time. The problem is that scouts will often come back having found multiple good sites, and so the swarm has to very quickly decide which of these options is the best one. They can’t afford to spend too much time deliberating, but at the same a bad choice could wipe out the entire colony.
Researchers P. Kirk Visscher of UC Riverside and Thomas Seeley of Cornell have discovered a crucial way in which bees come to these decisions as quickly as possible, and it actually precisely mimics what goes on with neurons in the complex brains of humans and other primates.
While the house hunting bees continue their figure eight dance, a different set of bees known as sender scouts will sometimes give them a “stop signal”, which is a short buzz punctuated by the sender butting her head against the dancer. This makes the dancing bee stop moving, and it allows the swarm to stop focusing on this repeated information and come to a better decision. Monkeys’ brains send out similar signals to inhibit their neurons while making decisions. Visscher comments on this similarity:
“It appears that the stop signals in bee swarms serve the same purpose as the inhibitory connections in the brains of monkeys deciding how to move their eyes in response to visual input. In one case we have bees and in the other we have neurons that suppress the activity levels of units – dancing bees or nerve centers – that are representing different alternatives. Bee behavior can shed some light on general issues of decision making. Bees are a lot bigger than neurons for sure, and may be easier to study!”
This phenomenon, known as cross inhibition, serves precisely the same function with bees that it does in nervous systems. It’s a way of avoiding decision-making deadlock when presented with a set of equally viable alternatives. Visscher explains:
“The message the sender scout is conveying to the dancer appears to be that the dancer should curb her enthusiasm, because there is another nest site worthy of consideration. Such an inhibitory signal is not necessarily hostile. It’s simply saying, ‘Wait a minute, here’s something else to consider, so let’s not be hasty in recruiting every bee to a site that may not be the best one for the swarm. All the bees have a common interest in choosing the best available site. This is critical, because the swarm must choose a single nest site, even if two sites of equal quality are available. This cross inhibition curtails the production of waggle dances for, and thus the recruitment of bees to, a competing site.”
For honeybees to choose a new home, a given site must attract a certain number of scout bees. Once it becomes clear that a “quorum” of scouts have settled on a single place, a piping signal goes through the swarm, telling the rest of the bees to prepare to fly. This is also where another round of stopping signals are sent to the dancing scouts, both those for and against the chosen site. Visscher explains:
“Apparently at this point, the message of the stop signal changes, and can be thought of as, ‘Stop dancing, it is time to get ready for the swarm to fly.’ It is important for the scouts to be with the swarm when it takes off, because they are responsible for guiding the flight to the nest site.”
While we don’t yet know just how precisely honeybees mimic our neurons, it’s a fascinating reminder of how a lot of the same basic structures can be found throughout nature, even in two groups as completely dissimilar as a swarm of honeybees and the neurons of the primate brain. This is quite possibly the craziest example yet of convergent evolution, if nothing else.
Science, 2011. DOI: 10.1126/science.1210361