(ORDO NEWS) — In 1963, Austrian entomologist Herbert Geran and German behavioral scientist Martin Lindauer noticed something special about the way honey bees move through the air.
When bees were trained to fly over a lake, they could only get to the other side if there were waves and ripples on the surface of the water.
If the lake was mirror-smooth, then the insects suddenly lost height until they crashed their heads into the liquid glass.
At the time, the findings supported the idea that honey bees use visual cues to navigate during flight, and subsequent research provided interesting new insights into the flight strategy of these talented little aeronauts.
By repeating the 1963 experiment, albeit in a more ethical fashion, the researchers showed that honey bees watch the ground passing under them to regulate their flight altitude.
The experiments were carried out in a rectangular tunnel 220 centimeters (87 inches) long, located in the open air, with mirrors on the ceiling and floor that could be closed to look like normal walls.
When all the mirrors were closed, the bees usually flew from one side of the tunnel to the sweet treat on the other side, maintaining a nearly constant height.
When the ceiling was pulled up to reveal a mirror that seemed to double the height of the tunnel, the bees easily made it through.
But when the floor became mirrored, which made the earth seem twice as far away, accidents began. The bees started flying normally, but after about 40 centimeters (15 inches) of flight, their height began to drop until the insects hit the glass bottom.
When the ceiling and floor were mirrored, creating a parallel pair of endless walls, the bees would begin to lose height, flying only about eight centimeters (three inches), and soon fall to the ground.
The results obtained are very similar to the spatial disorientation that sometimes affects pilots. When pilots can’t see ground speed, they struggle to maintain altitude.
Even during a graveyard spiral, the human senses can trick us into thinking we are still in level flight. This is why aircraft instruments are so important; they help us overcome spatial illusions and keep the aircraft at altitude even when there is no texture or shadow on the ground or water below.
Unfortunately, honey bees do not have such a back-up system to help them. Even when the mirror floor only existed in the second half of the tunnel, their steady flight from the first half was suddenly interrupted by a sharp fall.
“Interestingly, our double-mirror condition allowed us to approach the open-air flying conditions over calm water surfaces that [Geran and Lindauer] used,” write the authors of the new study.
“Our results are consistent with theirs to the extent that bees lose height in the absence of ventral optic flow.”
In short, it appears that bees use visual cues on the ground to maintain altitude, as opposed to visual cues in the sky.
When the ground stops giving the insects a proper baseline, the researchers believe they lower their altitude to see if they can regain this “ventral visual stream.”
Thinking he is further away than he really is, they end up crashing into the ground.
If the bees in the experiment were given a wider field of view, they could probably use other cues around them to help maintain their height. But when flying through a large, still lake or a closed tunnel, the insects have few alternatives for determining altitude.
Interestingly, a similar experiment showed that fruit flies do not use the ventral visual stream to control height. Therefore, different species may use different methods to maintain flight.
At high altitudes, people are often told not to look down for fear that we will fall. But if the honey bee had followed the same instructions, its downfall would have been inevitable.
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