Like a moth to a flame? New research shows insects aren’t drawn to light - they’re just confused

This 2022 photo provided by Samuel Timothy Fabian shows an Atlas moth used to test the interaction of flying insects with artificial light, photographed at ICL.
This 2022 photo provided by Samuel Timothy Fabian shows an Atlas moth used to test the interaction of flying insects with artificial light, photographed at ICL. Copyright Samuel Timothy Fabian via AP
By Christina Larson with AP
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Artificial lights are scrambling insects' navigational systems, new reserach shows.

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Like a moth to flame, many scientists and poets have long assumed that flying insects were simply, inexorably drawn to bright lights.

But that's not exactly what's going on, a new study suggests.

Rather than being attracted to light, researchers believe that artificial lights at night may actually scramble flying insects' innate navigational systems, causing them to flutter in confusion around porch lamps, street lights and other artificial beacons.

“Insects have a navigational problem,” says Tyson Hedrick, a biologist at the University of North Carolina at Chapel Hill, who was not involved in the research. “They're accustomed to using light as a cue to know which way is up.”

Artificial light causes confusion for insects

Insects do not fly directly toward a light source, but actually “tilt their backs toward the light,” says Sam Fabian, an Imperial College London entomologist and co-author of the study published Tuesday in the journal Nature Communications.

That would make sense if the strongest light source was in the sky. But in the presence of artificial lights, the result is midair confusion, not attraction.

For the study, researchers attached tiny sensors to moths and dragonflies in a laboratory to film 'motion-capture' video of flight - similar to how filmmakers attach sensors to actors to track their movements.

This 2022 photo provided by Samuel Timothy Fabian shows ongoing experiments on the effect of artificial light on wild flying insects in Monteverde, Costa Rica.
This 2022 photo provided by Samuel Timothy Fabian shows ongoing experiments on the effect of artificial light on wild flying insects in Monteverde, Costa Rica.Samuel Timothy Fabian via AP

They also used high-resolution cameras to film insects swirling around lights at a field site in Costa Rica.

This allowed them to study in detail how dragonflies will circle endlessly around light sources, positioning themselves with their backs facing the beams. They also documented that some insects will flip upside down - and often crash land - in the presence of lights that shine straight upward like search lights.

Insect flight was least disrupted by bright lights that shine straight downward, the researchers found.

“For millions of years, insects oriented themselves by sensing that the sky is light, the ground is dark" - until people invented artificial lights, says Avalon Owens, a Harvard entomologist who was not involved in the research.

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