Strange phenomenon when honey bees fly over the mirror

Experts fly honey bees through tunnels fitted with mirrors in the ceiling and floor, and then observe how they fly when the mirror is hidden or exposed.

In 1963, Austrian entomologist Herbert Heran and German behavioral scientist Martin Lindauer, discovered something unusual about the way honey bees fly. When a swarm of bees are trained to fly over a lake, they can only fly to the other side if there are waves and ripples on the surface. If the lake is as flat as a mirror, they will suddenly drop in height until they crash straight down.

A flying honey bee.

At the time, scientists thought that honey bees used visual cues to navigate when flying. New research in the journal Biology Letters adds interesting information about this creature's flight tactics, Science Alert reported on April 17.

Replicating the 1963 experiment, the French team showed that honey bees watch the rapidly drifting ground below to adjust their altitude as they fly. The experiment took place in an outdoor rectangular tunnel 220 cm long with mirrors mounted on the ceiling and on the floor.

When the entire mirror is covered, honey bees often fly from side to side of the tunnel to get food at a nearly constant altitude. When revealing the mirror on the ceiling made the height of the tunnel seem to double, the bees still easily flew through.

But when exposing the mirror on the floor made the ground look twice as far, collisions began to happen. At first the honey bee flew normally, but after flying about 40 cm, their altitude began to decrease until it hit the mirror. When both the ceiling and the floor are mirrors, the honey bees drop their altitude after flying by only about 8 cm and soon crash downwards.

This is a lot like the disorientation in space that sometimes happens to pilots. When it is not possible to determine the aircraft's speed relative to the ground, it is difficult for the pilot to maintain altitude.

Even in a "graveyard vortex" (a condition in which an aircraft descends, descending into the ground in a spiral), the senses can deceive people into still flying in a balanced manner. So the tools on the plane are extremely important. They help pilots overcome space illusions and keep the plane aloft even when there are no structures or shadows on the ground or water below.

Honey bees have no such system to help them escape. Even if the floor mirror only appeared in the second half of the tunnel, their steady flight in the first half was interrupted by a sudden plunge.

New research shows that bees seem to use visual cues on the ground to maintain altitude rather than visual cues in the sky. When the ground no longer provides a suitable baseline, bees will descend to see if they can restore it. They thought the ground was farther away than it really was, and eventually crashed.

If the honey bees in the experiment were given a wider visual field, they would probably use other cues around them to help maintain altitude. But when flying over a large flat lake or closed tunnel, there are very few options that they can use to measure altitude.