Why are insects attracted to light? Science has the answer

Have you ever been annoyed by a buzzing insect while you are scrolling your phone in the darkness? or a massive flock of these insects flying in an erratic path around street lights?

While we have known that insects fly at a level during the day, their flight path becomes completely unpredictable at night in the presence of artificial light. We have known that moths and insects are attracted to artificial light, but we had not known the mechanism behind it.

A team of researchers has now claimed to have understood the underlying navigational nightmare that attracts insects to that spec of light in the darkness and makes them go berserk.

While a long-standing theory has been that the insects consider the light to be coming from the Moon or a celestial object, which scrambles their navigational senses causing them to fly in a scattered pattern around the light. But the new explanation is much more scientific.

Biologists from the Imperial College London and Florida International University have explained that insects consider the artificial light to be coming from the open sky in the darkness and in that interpretation, they orient themselves along an up-and-down axis. The instinct then prompts them to roll back towards the light creating the seemingly erratic flight paths.

"Our guidance model demonstrates that they go into endless banking turns, sufficient to create the seemingly erratic flight paths of insects near lights and is the most plausible model for why flying insects gather at artificial lights," the team said in a paper uploaded to the bioRxiv server. It is yet to be peer-reviewed.

The team employed high-resolution motion capture in the laboratory and stereo-videography in the field to reconstruct the 3D kinematics of insect flights around artificial lights. They tracked the flights of dragonflies, butterflies, and moths flying around light bulbs in the lab and forests of Costa Rica.

They noticed that at times the insects would tilt upward into a stall, while at other times pass above the bulb flip upside down, and nosedive.

Entomologists have already known that insects could fly level in the daytime due to directional instincts and are able to keep their backs pointed toward sunlight. However, the new study reveals that they lose this ability in the presence of artificial light in the darkness.

Scientists have already warned that Insects around the world are rapidly declining due to rising artificial light. While Habitat loss, pesticide use, invasive species, and climate change have all contributed to the decline in insect numbers, critical for the balance of nature, "artificial light at night is another important, but often overlooked, bringer of the insect apocalypse."