For a long time, there has been a misconception about why flying insects are attracted to street lights. Conventional wisdom holds that flying insects are simply attracted to light sources. However, researchers have recently proposed a new idea, and they believe that the real reason for the attraction of flying insects is actually the environmental chaos caused by artificial light sources.
The invention of artificial light sources has made the environment in which insects live extremely complex. Because insects are naturally sensitive to light, they always feel that "the sky is bright and the ground is dark". This illusion creates a confusion in the sense of direction in the insect search for the light source. Instead of flying directly towards the light source, insects tend to "tilt their backs towards the light". The phenomenon was revealed by Sam Fabian, an entomologist at Imperial College London and co-author of a new study. He believes that this behavior is due to the natural reaction of insects to light.
In fact, this phenomenon makes sense if the light source is located in the sky. Because in the natural environment, insects will use the light from the sky to determine the direction and maintain a flight attitude. However, with the interference of artificial light sources, the situation has changed. Insects are constantly fluttering in mid-air, causing confusion in direction. The study, published in the journal Nature Communications, noted that insects with their backs to natural skylight help maintain proper flight attitude and control. This discovery reveals why flying insects exhibit chaotic flight trajectories in the environment of artificial light sources.
In modern cities, artificial light sources such as street lighting and billboards are ubiquitous, and these light sources have a significant impact on the behavior of insects. Recent studies have found that insects respond in the vicinity of artificial light sources by "creating a continuous turn around the light and trapping insects". This phenomenon has attracted the attention of biologists, who have studied this behavior of insects in depth. Tyson Hedrick, a biologist at the University of North Carolina at Chapel Hill, explains the phenomenon. "Insects have navigation problems," he said. They are accustomed to using light as a clue to know which path is up. "Light is a natural navigation tool for insects. At night, insects judge their position and direction based on the direction and intensity of the light, allowing them to find the right path.
However, the interference of artificial light sources makes this navigation method of insects challenging. Since the intensity and direction of artificial light sources can be very different from natural light sources, insects can produce chaotic navigation signals when they come into contact with these light sources. This causes the insect to produce a continuous turning behavior around the light, constantly trying to find the right direction. And this behavior just makes them easier to catch. In addition, Hedrick also points out that insects' dependence on light may also cause them to be more susceptible to disturbance near light sources. Because in the vicinity of a light source, an insect's visual system can be overstimulated, making it difficult for them to judge the right direction. This situation exacerbates the chaotic behavior of insects in the vicinity of artificial light sources to a certain extent.
The researchers also found that the insects' flight was minimally disturbed by bright light that was shining directly downward. This discovery has attracted the attention of the scientific community because it means that insects can maintain their flight path and sense of direction even when directly illuminated by a light source. Avalon Owens, an entomologist at Harvard University, provides an in-depth analysis of the findings. He said that the invention of artificial light has changed the living environment of insects, which has also indirectly affected the flight behavior of insects. "For millions of years, insects have positioned themselves by perceiving that the sky is light and the ground is dark," Owens explains, "and it's a biological instinct and key to insect survival." "However, the invention and use of artificial light, especially the strong light that shines directly downward, has interfered with this way of positioning insects. Bright light can confuse insects because they can't tell the direction of the light source. In this case, the insect's flight path can be affected and may even cause them to be unable to find their destination. This has a huge impact on the survival and reproduction of insects.
In this groundbreaking study, scientists have taken a novel approach to the flight behavior of moths and dragonflies. In the lab, they use tiny sensors to capture the movements of these tiny insects as they move through the air. This method is similar to the use of motion capture technology in filmmaking to record an actor's performance, thus accurately capturing every subtle movement.
Not only did the research take place in the lab, but the researchers also traveled to fields in Costa Rica to capture vivid images of insects circling around the lights using high-resolution cameras. This method of in-situ observation allows scientists to learn more about how dragonflies continuously rotate around a light source, providing a new perspective on the flight behavior of insects.
In addition, the researchers found some interesting phenomena in insects in the presence of direct light sources, such as searchlights. They found that some insects flew upside down and collided frequently during flight. This finding contributes to a deeper understanding of insects' flight adaptation in light environments and how they maintain their flight balance in complex environments.