Theories such as “moon navigation” and “flight to light” have explained why nocturnal insects fly erratically around fires and lamps. However, the cause of this strange behavior remains to be resolved, as he lacks three-dimensional flight data to rigorously test these theories.
A new study by researchers at Imperial College London uses high-resolution motion capture in the laboratory and stereo videography in the field to reconstruct the 3D kinematics of insect flight around artificial light. Did. They shot slow-motion video and analyzed it to gain new insights into why nocturnal insects gather around lights.
Researchers found that flying insects are not attracted to the light, but instead assume that the light is the sky and therefore a path “up”, causing them to become disoriented, which causes them to crash. did.
Dr Samuel Fabian, from Imperial University’s School of Biotechnology and lead author of the study, said: “We wanted to understand why insects cannot resist flying into and around potentially deadly light sources. It may help us better understand the impact.”
In a field experiment in Costa Rica, researchers used video analysis to find that, contrary to existing theory, insects are not attracted to light from a distance. Instead, they become trapped when flying near artificial light sources.
This study revealed that insects face the dorsal (top) side toward the light source. This helps maintain good flight control in natural light, but when approaching artificial light it ends up maneuvering around the light source and becoming continually trapped.
In addition, the researchers observed three unusual behaviors: circling (a steady circular flight around the light), stalling (a sudden jump that gradually reduces speed until no movement is observed), and reversals (the insect flips over). return and crash). Insects often stand up under the light, even if it leads to a collision, repeating the process of climbing onto the light and inverting again, consistently pointing their dorsal axis toward the light source.
Researchers from the lab at Imperial College London attached location markers to five species of insects: the darter dragonfly and the migratory hawker dragonfly, the yellow underwing and low-winged atlas moth, and the oleander moth. Motion capture cameras tracked movement around various light sources, including UV LED bulbs, UV-Blue light tubes, and cool-white LED bulbs.
The study found that the light source has a significant effect on the insect’s ability to control orientation, particularly its ability to lean toward the light.
The researchers used computer modeling to analyze insect behavior. They decided that leaning toward the light was enough to explain the seemingly erratic flight patterns observed near the light. The researchers say this model is the most plausible explanation for why flying insects are attracted to artificial light.
Dr. Fabian said: “Flying animals especially need a reliable way to determine their orientation relative to the direction of gravity.
“With the help of new technology that allows us to track the movements of small insects under difficult and dark conditions, we were able to understand how these insects behave around different light sources.”
There has been a significant increase in artificial light at night, including streetlights, residential and commercial building lights, and vehicle lights. Researchers believe that minimizing unnecessary unobstructed upward light and ground reflections can reduce their impact on night-flying insects, especially when artificial light sources overwhelm natural light from the sky. He emphasizes that it can be reduced.
Dr. Fabian added: “I hope this study makes us think again about the light we cast at night. Light at night is pollution and we have to think of it that way. Just by covering it up and limiting it. , could dramatically improve the lives of nocturnal wildlife.
“The next important step in this research is to understand how the night-time light effect changes with distance. We can tell what’s happening at 1 meter from the light, but we can’t see what’s happening at 100 meters. Is that happening?”
- Fabian, S. T., Sondhi, Y., Allen, P. E., et al. Why flying insects are attracted to artificial light. Nat Commun 15, 689 (2024). Doi: 10.1038/s41467-024-44785-3