How Does a Bee Give Directions? A Figure of Eight on a Vertical Comb
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A returning forager performs a repeated movement on the comb whose angle and duration encode the direction and distance of a food source. Decoding it took decades and the interpretation was disputed for longer.
What the dance encodes
A forager that has found a worthwhile source returns to the hive and performs a movement in which it walks a straight run while vibrating its body, then circles back to the start and repeats, alternating the side it circles on so the path traces a figure of eight. Two quantities are encoded in the straight run. The angle of the run relative to vertical on the comb corresponds to the angle of the food source relative to the sun as seen from the hive, so a run straight up means fly towards the sun. The duration of the run corresponds to the distance, with longer runs meaning further away. Other bees follow the dancer closely, and some then fly out and find the source.
What else is conveyed
Several further elements have been identified:
- •A simpler round dance for nearby sources, which conveys distance without direction
- •Vigour and repetition, which correlate with how good the source is
- •Odour carried on the dancer's body, which identifies what to look for
- •Sounds produced by wing vibration during the run, which followers detect
- •Stop signals from other bees, which discourage recruitment to a source with a problem
- •The same dance used to communicate about potential nest sites when a swarm is choosing
How it was worked out
Karl von Frisch established the interpretation over several decades from the 1920s, working by marking individual bees, training them to feeding stations at known positions and distances, and recording what the returning bees did and where the recruits went. The correspondence between dance angle and food direction emerged from thousands of such observations. He shared a Nobel Prize in 1973 for the work. The interpretation was seriously challenged in the 1960s by researchers arguing that recruits were finding the food by odour rather than by decoded directions, which prompted decades of further experiment, and the question was settled largely by studies that tracked individual recruits by radar and found them flying the direction and distance the dance specified, including when the dance had been manipulated.
Whether every bee uses it
The dance is not the only recruitment mechanism and its importance varies more than the textbook account suggests. Many foragers that follow a dance do not fly out, and many that do arrive well off target and locate the source by odour over the final stretch. Experienced foragers with a known productive site largely ignore dances. In some conditions, notably when food is abundant and nearby, the dance contributes little to overall foraging success and colonies perform comparably when it is disrupted, while in patchy environments with scarce distant resources it matters substantially, which experiments comparing disrupted and normal colonies in different habitats have shown directly. Related bee species differ in their dances and some stingless bees use scent trails instead, which is a different solution to the same problem.
What it took to correct for
The system involves compensations that make it more impressive than a simple mapping. The sun moves across the sky, so a bee dancing for a source found an hour earlier must adjust the angle for the sun's movement in the interim, which it does using an internal clock. A bee that cannot see the sun uses the pattern of polarised light in the sky, which indicates the sun's position through cloud. Distance is judged by how much the visual scene flows past during the outward flight rather than by energy used, which was established by making bees fly through narrow patterned tunnels that exaggerated the flow and caused them to dance for a far greater distance than they had travelled. Wind and terrain introduce errors the system does not fully correct.
The takeaway
The angle of the straight run relative to vertical corresponds to the food's direction relative to the sun, and its duration corresponds to distance. The interpretation was established by marking individuals and training them to known stations, challenged on the grounds that recruits used odour, and confirmed by radar tracking of individual recruits. Bees correct the angle for the sun's movement using an internal clock.