Scientists finally understand why insects are drawn to artificial light

Thousands of moths swarm around flood lights at the Newcastle United Jets home game at Energy Australia Stadium in Newcastle, 1 October 2005. (Photo by Fairfax Media via Getty Images via Getty Images)

It's a saying that has been used for centuries: Like a moth to a flame. But has anyone asked why moths are attracted to light? 

Finding a graveyard of moths inside a lamp is a common annoyance for any homeowner. But the actual reason these sources of light attract moths is not as common as you might think. 

According to a study published on January 30 in the journal Nature Communications, 

Moths aren't literally attracted to sources of light but rather get disoriented and trapped from the orbit of artificial light, according to scientists. 

Scientists believe that artificial light screws with a flying insects' innate navigational systems, causing them to flutter in confusion around porch lamps and other artificial beacons. 

Researchers used motion-capture cameras and infrared illumination to show how insects like moths interacted with various light sources.

They found that since insects have been known to keep their backs pointed to the brightest direction – usually the sky – it has helped bugs use this evolutionary advantage to aid them in their flight patterns at night. 

"Insects in the air don’t inherently know which way is up, they don’t have a very good way of measuring that," said co-lead study author Samuel Fabian.

It’s assuming the light is the direction of up, but it’s wrong. And if you tilt, that’s going to create sort of weird steering patterns, in the same way that if you were riding a bike and you tilt over to one side, you’re going to get to steer in a big circle, it’s all going to go a bit funky," Fabian added. 

So once an artificial light source is added to the mix, it throws the bugs off completely sending them into a daze not knowing which direction they are going inadvertently making us think they are flying towards the light like zombies. 

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.

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, said Avalon Owens, a Harvard entomologist who was not involved in the research.

The Associated Press contributed to this story.