LIGHT POLLUTION | Insects ‘lose their way’ at night due to artificial light

Artificial light drives insects completely crazy. Light bulbs, fire and streetlights cause butterflies and moths to flutter around them in erratic circles that are nothing like the behavior that these small animals acquire during the day.

It has often been believed that these animals are attracted to the light, but thanks to a detailed study it has been possible to find the real reason for this nocturnal frenzy: lInsects ‘lose their way’ when they cannot see the light of the stars.

And you only have to observe the movement of a moth during the night to understand that something is not right. Well, instead of fluttering around to get food or hide from the sight of predators, these little insects seem to be caught up in the black hole of fluorescent light.

This behavior caught the attention of a group of researchers from Imperial College London, who did not understand how the graceful movements of these animals could be captive by an insignificant light.

They are not the first to have wondered what could motivate this strange behaviour. For decades, all kinds of theories have been considered that could explain why insects go crazy when night falls.

Light pollution in the Iberian Peninsula. EFE

One of the first ideas was that they could be attracted to the heat of flames. But the hypothesis was soon discarded because many of the insects that had this behavior were not pyrophiles and, in fact, they are better attracted to cooler lights.

With your back to the light

Later the idea was established that these animals are genuinely attracted to light, in response to the ability of phototaxis. However, this answer does not serve to explain the movement of all the insects that approach the lights because, if it did, they would always end up colliding with the source of illumination. Therefore, it does not explain the erratic movement in circles.

But after carrying out several experiments, the results of which have been published in ‘Nature Communications’, it has been demonstrated that These strange behaviors are related to the ability of flying insects to maintain balance.

And the researchers verified that this movement in circles around a light bulb always happened in a curious way: the butterflies always turned their backs to the light. “It is what is called dorsal light”says Samuel Fabian, lead author of this study in an article published in ‘The Conversation’.

Moths attracted to the light of a light bulb. Pexels

Under natural conditions, it is the light in the sky – much brighter than that emitted by the ground – that guides the insects.which use their wings to know the proper orientation to fly.

Because these small animals, unlike the larger ones, They lack senses that allow them to notice in which direction the force of gravity is pushing to maintain balance.

The researchers studied the trajectory that the moths took when they encountered light from bulbs in the laboratory. The scientists were extremely surprised that the animals never collided with the light source because this movement did not fit with any physical model described so far.

Strange flight patterns

“We decided to make high-speed videos to determine flight trajectories and body postures with great precision,” explains Fabian, who reveals: “we discovered that its flight patterns did not closely match any existing model”.

The researchers saw how different insects pointed with their backs towards the lighteven going so far as to do complicated pirouettes to always maintain that position. “These orbital trajectories were just one of the behaviors we observed,” says Fabian.

This phenomenon has highlighted a serious problem that the planet suffers due to artificial light. Light pollution affects astronomical observation, deprives the population of seeing the night sky –almost a third of the world’s population lives in places where the Milky Way is not visible–, It can cause problems when falling asleep, causes fatal shocks to some species of birds and can even cause baby turtles to get lost before reaching the sea.. This new discovery adds a new problem to the long list.

“Insects trapped around a light seem to get the worst of it,” insists the researcher, who highlights that This behavior deprives them of food, exposes them to predators and tires them so much that they can die of exhaustion..

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