Why do insects love night lights so much?

The suicidal insect flying towards the light at night is a long-established poetic image, even Palasi refers to himself.

“Like a veil between the flame of a candle

Deliberately attacks himself

Don’t think it’s the heat of a candle flame

It also burns”.

However, scientists still cannot agree on why some insects do this. Although there is no widely accepted explanation, there is a technical term for it: what do these butterflies and already flying insects do? Positive phototaxis. In protocol, movement dictated by some stimulus is called taxis, in the case of phototaxis this stimulus is mild. A positive indicates that these animals move in the direction of the stimulus. Of course, there is also negative phototaxis, when animals avoid light, ​​for example, cockroaches do this when we turn on the lights in the kitchen at night, or wasps (also known as cellar bugs) when we turn a rotting log.

The formation and cause of negative phototaxis is easy to explain: darkness is good because you can avoid predators, and there is also a pleasant humid environment – light, on the other hand, represents a dangerous and unpleasant environment. The positive version crack is a tough nut to crack. There are many explanations for this phenomenon, and one or the other may be true for different cases. When it comes to the origin of positive phototaxis, it should be kept in mind that night light is primarily a product of human civilization. Before there were candles, candles and lanterns, the only light at night was the moon and the stars, so the behavior of nocturnal insects must have adapted to these light sources – only a blink of an eye in evolutionary terms for a few thousand years since humans illuminated the nights. This is also evident from the fact that insects insist on flying towards the light, which is particularly harmful to them.

One commonly accepted explanation is that for nocturnal insects, bright light is a clear way out of an enclosed space or escape route from a distressing situation. In the days before artificial lighting, if an insect flies toward the light at night, you can be sure it has a clear path, which is primarily important in tight situations where you need to escape. This could be explained when moths or other nocturnal insects fly into the candle flame like kamikazes.

However, not all insects come to light in this way, and some hover around for long periods of time. There was another explanation for this behavior. Accordingly, for night-flying insects, strong light, the moon or, in its absence, the stars play a role in maintaining flight direction. If an insect always flies at the same angle to the light source—its relative position changes very little because the moon is so far away—the flight is in a straight line. However, the situation is completely different if the light source is close, because as the animal flies past it, the angle of incidence of the light also changes. If it wants to keep the angle constant, it will circle the light in a spiral path, the end of which is the light source. There is also a simple explanation for circling, simply positive phototaxis, where the amount of light detection acts to determine the frequency of wing beat. So, if the light source is close, the intensity of the light perceived by the two eyes will be different, so one wing will beat more strongly than the other, causing such a circular motion.

There is also the idea of ​​which insects use the moon for orientation in a different way. This helps them stay up in the sky, so you know which direction is up and down – and they try to fly so the light is always above them. There are also theories as to why insects return to light even when they are able to leave. Like humans, insect eyes are known to adapt to light intensity, but it adapts much more slowly from light to dark than from dark to light. As a result, when they leave the light, they are effectively blinded and disoriented for a short period of time, so they return to the light. There is also an explanation for why insects often settle in lamps (unless, of course, it is as hot as a candle). The sudden bright light is thought to drive diurnal behavior, which in the case of nocturnal insects is restful sleep.

There are more complex theories. For example, some female moths release pheromones that emit a very weak infrared light when excited, and emit lights at this wavelength very strongly, thereby ensnaring unfortunate male moths in a sex trap. In addition to the theory, they also present the argument that more men than women come to light. However, this line of thinking does not explain why females also fly toward the light, or why creatures without such pheromones also fly toward the light. Critics of the theory argue that, among moths, males also move and fly more anyway, so it’s not surprising that they fly more toward the light. Additionally, insects are actually attracted to UV light and don’t really care about yellow light.

It may also be that whether insects are attracted to light does not even depend on their sex. It may be noticed that young people are generally the majority of those who fly towards the light, and more than once you will see the old ones happily feasting on the flowers next to the lamp, unconcerned by the bewitching light. Based on this, it is assumed that young individuals initially use the moon primarily for orientation, but once they develop a kind of mental map of their surroundings, they no longer need it. It is also well established that this behavior is often reversed in females during spawning and they are light-avoided.

Whatever the exact reason, artificial light can be dangerous to protected insects. For example, bees fly to roadside lights instead of water surfaces where they cannot naturally lay eggs. For this reason, a few years ago, a special light barrier protecting pedestrians was installed on the Tildy Zoltán bridge in Tahitótfalu, which will also be installed on the Árpad bridge this year.

proof’s: He did | Science Friday | Missoula Butterfly House