- Scientists at Imperial College London say insects see light as pointing ‘up’
- 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 are attracted to artificial light.
But experts think they may have solved the puzzle – and you might even feel sorry for the insects.
For years, scientists have believed that insects interpret artificial light as an escape route or that insects are blinded by the light source.
Now it appears that they can get dizzy from bright lights and eventually become 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 range of insects, including moths, dragonflies and fruit flies.
For years, scientists have believed that insects interpret artificial light as an escape route or that insects are blinded by the light source.
Now it appears that they can get dizzy from bright lights and eventually become completely disoriented
Analysis showed that insects appear to confuse bright light with the direction ‘up’.
During the day this makes flying easy as they keep their backs tilted to the clear sky and can maintain a stable flight path that is correctly aimed at the horizon.
But artificial light causes them to fly erratically, causing the creatures to constantly correct their flight path, resulting in dizziness in insects and what we see as an attraction to artificial light.
Author Samuel Fabian said: ‘We think the strange flight is due to insects confusing the light for the direction of ‘up’.
‘Insects have been flying around for 370 million years, the sky has almost always been clearer than the ground.
‘Insects, including other animals including fish, use the brightest area as an indicator of where the sky is and therefore which way is up.
‘Knowing which way is up is critical to flying, because you must direct the forces of flight to cancel out the acceleration due to gravity.
‘However, we have started to ruin this general rule by creating bright lights at night.
‘Insects think these bright spots are the sky and tilt their backs towards them to focus their flight forces on where they think gravity should be.
Author Samuel Fabian said: ‘For 370 million years, insects have been flying around, the sky has almost always been brighter than the ground. However, we have started to ruin this general rule 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’re wrong about where gravity is and this imbalance leads them down all kinds of strange flight paths.
‘The most obvious example of this is insects flying directly over lamps, turning themselves upside down and falling to the ground.
‘Insects cannot directly measure gravity accurately while in the air, because they perform all kinds of accelerations that feel the same as gravity and are indistinguishable from each other.
‘Using the direction of the light is a beautifully simple way to solve this problem. Until someone starts putting big street lamps everywhere at night.’
The findings have been published in the journal Nature Communications.