New explanation: Why do insects revolve around light?
What makes bulbs attractive to insects? Several explanations for this have been proposed so far. High-speed cameras are now showing what might actually be the cause.
© Alessandro Della Bella/Keystone/Image Alliance (clip)
Insects gather around lights. A reflex used to control flight posture prevents them from escaping bright light, a team of researchers says.
since Homo sapiens When artificial light is provided at night, a mysterious behavior is also observed in the animal world: in a seemingly suicidal manner, insects from the surrounding area swarm around the light source and either burn in the fire or circle the bright spot until they collapse from exhaustion. A group of researchers have now proposed a new explanation for this, which they discovered with the help of high-speed cameras and motion-capture sensors.
The back light reflex is responsible, The team writes in the specialized magazine “Nature Communication”.: The reflex usually causes animals to always line up so that their backs point toward the brightest point in the area. In this way, the insects can adopt a horizontal flight position, because the brightest place is usually the night sky – but not when a person turns on a flashlight.
Hence the brightest part of the environment is the point light source. The reflection then causes the light to rotate forever. The group led by Samuel Fabian of Imperial College London and Yash Sondhi of Florida International University in Miami observed this distinctive flight maneuver — back toward the light, legs outward — using their camera technology, even in groups of insects that don't normally travel at night. , such as dragonflies or butterflies.
They found no evidence in their records for the more common alternative explanations. It was said, for example, that insects confuse lamps with the moon, and use them as an aid to navigation. They are attracted to the heat emanating from the lamp; They see their escape route in the light; They were blinded by the bright light and thus disoriented. However, all of these approaches do not explain the distinctive flight stance and non-stop rotation, explains the team behind the study. If the insects mistaken the lamp for the moon, they would have to spiral toward it, which Fabian, Sunde and colleagues have not observed for now.
Reflexive acrobatics
Additional evidence for the role of the dorsal light reflex: If the light source is on the ground, the insects often make a 180-degree longitudinal turn and then either continue to fly with their backs down or crash directly into the ground, the team explains. .
It cannot be said with certainty whether reflex alone is sufficient to fully explain this phenomenon. Other factors may also play a role, for example if the insect is far from the lamp. However, the study provides no evidence that insects are actually attracted to light in any way. The study's authors therefore assume that the animals only fall under the lamp's spell by chance and then remain trapped there.
For their experiment, they allowed the animals to fly in a controlled laboratory environment, but they also studied the behavior of insects in the wild. Only thanks to modern, highly light-sensitive camera chips has it become possible to capture slow-motion shots even at night. This now allows lightning-fast flight maneuvers to be seen.
When an insect is tossed into the air in windy conditions or fly maneuvers involve strong lateral acceleration, a simple sensation such as the light dorsal reflex helps maintain direction. In such cases, gravity is of little use as a guide. However, the reflex is by no means the only mechanism that insects use to control their flight mode. It also happens that in the natural environment, for example at sunset or at the edge of a forest, the bright spot is not directly above the animal. The study's authors don't know why — or if at all — insects still line up parallel to the ground, they write in their post.
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