How bees navigate

The sun compass

A bee's primary reference is the sun's position, and she compensates for its movement across the sky using an internal clock. A bee held in the dark for two hours and then released will still fly the correct bearing, having corrected for where the sun has moved to in the interval.

This is also what makes the waggle dance work. The dance is performed on vertical comb in a dark hive, and the angle of the waggle run from vertical translates directly into the angle of the flight path from the sun.

The polarised light backup

On a cloudy day the sun's position can still be inferred from the pattern of polarised light in the sky, which a bee reads through specialised receptors in the upper part of her compound eyes. A patch of blue sky the size of a hand is enough to fix the sun's position and keep the compass working.

Landmarks and the memorised route

Beyond the compass, a forager memorises the landscape. On her first flights from a new hive she performs orientation flights — hovering in widening arcs facing the entrance, learning what it looks like and where it sits relative to nearby features.

This is why moving a hive a short distance causes problems. Move it two metres and returning foragers will cluster at the old location; move it three kilometres and they will reorientate correctly. The rule of thumb among beekeepers is less than a metre or more than three kilometres, and the reason is that the bees are navigating to a remembered place rather than following the hive.

The odometer

Bees measure distance by optic flow — how much the visual scene streams past as they fly. This was demonstrated by flying bees down a tunnel patterned to exaggerate or reduce the apparent flow, which caused them to over- or under-report distance in their subsequent dances by a predictable amount.

It is an elegant system with a known failure mode: a bee flying over featureless water or a smooth surface underestimates the distance travelled, because there is less visual texture streaming past.

Putting it together

• Sun compass, corrected by an internal clock, for direction.
• Polarised light patterns as a backup when the sun is obscured.
• Memorised landmarks for the final approach and the hive location.
• Optic flow for distance.
• Scent for the last few centimetres, both flower scent and the colony's own.