The brain of a honeybee is tiny — the size of a pin head — and contains less than a million neurons, compared to the 85 billion in our own brains. Yet with that sliver of brain, bees can do some extraordinary things. They can count and interpret abstract patterns. Most famously, bees have the ability to communicate the location of flowers to other bees in the hive.
When a foraging bee has found a source of nectar and pollen, it can let others in the hive know by performing a peculiar figure-of-eight dance called the waggle dance. The information contained in the waggle dance was first decoded by Austrian biologist Karl von Frisch, who picked up a Nobel Prize for his discovery in 1973. The dance in itself is not as complex as true language, but it’s remarkable in that it’s a symbolic form of communication.
Recently, Hiroyuki Ai at Fukuoka University has made another breakthrough in our understanding of this extraordinary behavior, by investigating the neurons that allow bees to process the dance information. Bees get information from hearing the dance, as well as seeing it. During the dance, bees vibrate their abdomens as they run in a figure-of-eight pattern. These vibrations send out pulses that are picked up by an organ on the antennae called Johnston’s organ. Johnston’s organs are equivalent to our ears.
Ai maintains hives of honeybees on the campus of Fukuoka University. (Incidentally, he says they have monthly meetings to discuss their research with students, after which they have tea parties and eat the honey produced by their bees.) Until recently, there has been very little understanding of how the bee brain deciphers the information encoded in the waggle dance. The reason, he says, is that bees only perform the dance in the hive, and it’s difficult to get them to do it in the laboratory.
It makes sense that the bees pay attention to sound. “In a dark hive, they can’t see the dance,” Ai says. “Honeybees hear the dance.” Honeybees are very sensitive to vibration, so mimicking the noise of a waggle dance can cause bees to journey to the same place indicated by a real dance.
Ai and his team recorded the vibrations made by the waggle dance, simulated the noises and applied the vibrations to the antennae of bees in the lab. This allowed them to track which neurons fired in response to the waggle dance, and follow their route in the insect brain.
The team discovered three different types of “interneurons.” These are connecting neurons that allow communication between different parts of the brain. Ai, along with team members that include Thomas Wachtler at Ludwig-Maximilians University in Munich, Germany, and Hidetoshi Ikeno of the University of Hyogo in Himeji, traced the path of interneurons in the part of the brain concerned with processing sound. They found that the way the interneurons turn on and off is key to encoding information contained in the waggle dance about distance.
This mechanism of turning on and off — in neuroscience it is called “disinhibition” — is similar to one used in other insects. For example, it’s how crickets listen to the songs of other crickets as well as how moths assess the distance from the source of a smell their antennae have picked up. Ai and his team suggest there is a common neural basis in the way these different species do things.
Communication is the key to forming complex societies. It’s what allows the honeybee to perform such extraordinary behaviors. And, naturally, language is a key factor in human success. Intelligence is required for both these things, so does this mean honeybees, with a minuscule brain, are intelligent? It’s a tricky quality to define. One attempt, from the American Psychological Association Task Force on Intelligence, defines it as the ability “to adapt efficiently to the environment and to learn from experience.” Bees are able to do this.
There are six different kinds of dance, for example, and bees are able to learn and change their behavior accordingly. If bees encounter a dead bee at a flower, they change the pattern of dancing they perform back at the hive, suggesting they can perform a risk/benefit analysis.
Both bee and human language are a consequence of intelligence, and research such as Ai’s forces us to rethink what we mean by intelligence. “There might be a common brain mechanism between humans and honeybees,” he says.
What it certainly shows is that you don’t need a big brain to be smart. As with many things, Charles Darwin realized this, writing in 1871: “The brain of an ant is one of the most marvellous atoms of matter in the world, perhaps more so than the brain of man.”
Rowan Hooper is managing editor of New Scientist magazine. He tweets at @rowhoop and his new book, “Superhuman,” is out next year.