The waggle dance

The code

• Direction: the angle of the straight waggle run away from vertical equals the angle of the target away from the sun's bearing. Straight up means fly towards the sun.
• Distance: the duration of the waggling portion encodes it, on the order of a second per kilometre, with the calibration differing between species and subspecies.
• Vigour: a richer source produces a longer, livelier dance with more circuits, which recruits more followers. This is not a third coordinate; it is how the colony weighs one source against another.
• Time correction: the sun moves while a bee is inside, and a dancer adjusts the angle to compensate. She is correcting for elapsed time without being able to see the sky.

The substitution of gravity for the sun is the part that startled everybody. Inside a dark cavity there is nothing to point at, so the dancer transposes a solar bearing onto a gravitational one. Open-nesting species that dance on a horizontal surface in daylight simply point at the target, which is almost certainly the ancestral form and makes the transposition look like what it is: a solution to nesting in the dark.

How the distance is measured in the first place

A dancer is reporting a distance she has to have measured. She does it by integrating optic flow — how much the image of the ground slid past beneath her on the outward flight — rather than by tracking time or energy. The demonstration is elegant: bees flown to a feeder through a narrow tunnel lined with a busy pattern experience far more image motion than the real distance warrants, and they come home and dance a much longer distance than they flew.

How followers read it

It is dark inside a nest, so nobody is watching. Followers press against the dancer and detect her vibrations through the comb and the air jets from her wing movements, using Johnston's organ in the antennae. A follower typically attends several circuits, often of more than one dancer, before leaving.

Decoding is imperfect. Recruits arrive spread around the indicated point rather than at it, and many leave without having extracted a usable vector at all, then search or follow scent instead. The angular scatter in the dance itself has been argued both ways — as an adaptive spread that samples a patch rather than a point, and as a physical limit on how precisely a small animal can perform a run on a comb. Neither reading is established.

The controversy, and how it was settled

Karl von Frisch decoded the dance over decades and shared the 1973 Nobel Prize in Physiology or Medicine for it. From the 1960s a serious challenge argued that recruits were not using the dance at all: they were leaving the nest and finding food by odour, and the correlation between dance and arrival was an artefact of foragers and recruits using the same scent cues.

That was a reasonable objection and it took thirty years to answer properly. The answer came from harmonic radar, which allowed individual recruits to be tracked in flight. They flew the vector encoded in the dance, including when experimenters displaced them so that the vector pointed somewhere they had never been. The dance carries usable spatial information, and odour still matters, and the two were never exclusive.

Dialects and species differences

The relationship between waggle duration and distance is not universal. Different Apis species, and different subspecies of the western honey bee, use different calibrations — one species' one-second run means a different distance from another's. Colonies made up of mixed subspecies misread each other's dances in the way you would expect from a mismatched conversion factor.

That is the strongest evidence that the dance is a code with parameters rather than a fixed reflex, and it is also the most direct route into a genuinely open question: how much of the calibration is genetic and how much is set by the environment a colony forages in.

What the dance is used for besides food

• Water sources, when a colony needs water for evaporative cooling.
• Resin sources for propolis.
• Candidate nest sites, danced by scouts on the surface of a settled swarm rather than inside a nest.

The nest-site use is the one that turns the dance from a foraging tool into a decision procedure. Scouts advertise competing cavities, dance vigour tracks quality, and the swarm converges on one option. That process is covered separately.