- Scientists at Imperial College London say insects see light as the “up” direction
- As a result, artificial light causes them to fly erratically and correct their flight path.
One of the enduring mysteries of science is why flies gravitate toward artificial light.
But experts believe they may have solved the puzzle, and might even make you feel sorry for the insects.
For years, scientists have believed that insects may be interpreting artificial light as an escape route or that the light source blinds them.
Now, it looks like they could be suffering from vertigo from the bright lights and end up completely disoriented.
A team from Imperial College London used high-speed infrared cameras to track the flight of insects, both in their natural environment and in a laboratory.
They examined a variety of insects, including moths, dragonflies and fruit flies.
For years, scientists have believed that insects may be interpreting artificial light as an escape route or that the insects are blinded by the light source.
Now, it looks like they could be suffering from vertigo from the bright lights and end up completely disoriented.
The analysis revealed that the insects seem to confuse bright light with the “up” direction.
During the day, this makes flying easier as they keep their backs tilted toward the bright sky and can maintain a constant flight path oriented correctly with the horizon.
But artificial light causes them to fly erratically, causing the creatures to continually correct their flight path, causing vertigo in the insects and producing what we consider an attraction to artificial light.
Author Samuel Fabian said: “We think the strange flight is due to the insects mistaking light for the direction “up.”
«For 370 million years insects have been flying, the sky has almost always been brighter than the ground.
‘Insects, among other animals including fish, use the brightest region as an indicator of where the sky is and therefore which direction is up.
«Knowing which direction is up is essential for flying, since the forces of flight must be directed to cancel the acceleration due to gravity.
“However, we have started to mess up this general rule by creating bright lights at night.
“Insects think these bright spots are the sky and lean their backs toward them to redirect their flight forces toward where they think gravity should be.
Author Samuel Fabian said: “For 370 million years insects have been flying, the sky has almost always been brighter than the ground. However, we have started to mess up this rule of thumb by creating bright lights at night.
A team from Imperial College London used high-speed infrared cameras to track the flight of insects, both in their natural environment and in a laboratory.
‘Unfortunately, they are wrong about where the gravity is and this imbalance leads them to all sorts of strange flight paths.
“The most obvious example of this is when insects fly directly over the lights, turn around and fall to the ground.
‘Insects cannot accurately measure gravity directly while in the air, as they exert all kinds of accelerations that feel the same as gravity and are indistinguishable.
«Using the direction of light is a very simple way to solve this problem. That is until someone starts putting up big street lights everywhere at night.
The findings were published in the journal Nature Communications.