An international team of scientists from the US, UK and Costa Rica has uncovered the secret behind why moths and other flying insects circle street lamps and other light sources at night. The study was published in the scientific journal magazine Nature Communications (NatComms).
It was previously believed that moths were attracted to the heat of the flames. This is partly supported by the fact that some insects are indeed pyrophyllous: They are attracted to fire and have learned to exploit recently burned areas. However, most of the creatures born do not belong to this category.
Another theory was that moths need light. This reaction is called phototaxis. Insects try to avoid darkness, but in this case their clusters will crash into lanterns and lamps instead of flying around them.
Another hypothesis suggested that insects confuse night light with moonlight, which moths and butterflies use to navigate at night. At the same time, creatures fly near bright objects along trajectories that do not fit such a pattern.
To study this question, researchers filmed insects flying around different light sources to accurately determine their direction of movement. When the videos were examined, it was seen that the moths were trying to turn their backs to the light. This is a known behavior called dorsal light response.
It turns out that orbital trajectories are just one of the observed moments. When insects fly directly under the light, they often lean upward as the light passes behind them, keep their backs to the lamp, and eventually fly straight up, stop, and dive backwards. Even more interesting was that when flying directly over the light source, the insects tended to turn upside down, turning their backs to the light again, but then abruptly descending.
Before the advent of modern lighting, the sky was generally brighter than the ground day and night, thus serving as a fairly reliable signal for a small, active flyer hoping to maintain a constant orientation. Experts note that artificial lighting, which sabotages this ability of insects by causing them to fly in circles, appeared relatively recently.
The researchers say their findings highlight the need to reduce light pollution to preserve insect diversity.
Biologists before warned It’s about the decline of insect populations around the world.