WASHINGTON (AP) — Like a moth to a flame, many scientists and poets have long assumed that flying insects are simply attracted to bright lights.
But that's not exactly what happens, a new study suggests.
Instead of being attracted to light, researchers believe that artificial lights at night may confuse the flying insects' innate navigation systems, causing them to flutter in confusion around porch lights, street lights and other artificial beacons.
“Insects have a navigational problem,” said Tyson Hedrick, a biologist at the University of North Carolina at Chapel Hill, who was not involved in the research. “They used to use light as a cue to know which way to go up.”
Sam Fabian, an entomologist at Imperial College London and co-author of the study, said the insects do not fly directly towards the light source, but in fact “tilt their backs toward the light.” Study published Tuesday In the journal Nature Communications.
This would make sense if the strongest light source was located in the sky. But in the presence of artificial lights, the result is atmospheric disorientation, not attraction.
For the study, the researchers attached small sensors to moths and dragonflies in the laboratory to film “motion capture” video of flight — similar to the way filmmakers attach sensors to actors to track their movements.
They also used high-resolution cameras to photograph insects hovering around lights at a field site in Costa Rica.
This allowed them to study in detail how dragonflies circle light sources endlessly, positioning themselves to face the rays. They also documented that some insects turn upside down — often hitting the ground — in the presence of lights shining straight up like spotlights.
The researchers found that the insects' flight was least disrupted by bright lights that shine downward.
“For millions of years, insects oriented themselves by sensing that the sky is bright and the ground is dark” — until people invented artificial lights, said Avalon Owens, a Harvard University entomologist who was not involved in the research.
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