The classic summer cookout comes with chips and drinks and then, after the sun goes down, swarms of insects flutter around the porch lights. But flying around artificial lights can have deadly consequences for critters like moths, mosquitoes, and gnats. They can get stuck under lampshades and be exposed to predators such as beetles, spiders, bats, and birds.
This “dumb spin” can distract insects from goals like eating, mating, and reproduction, said Harvard associate Avalon Owens. Artificial lights may contribute to this Decreased insect numbers all over the world. So, given the risks, why are insects so attracted to artificial lights?
Theories abound. Maybe mites Use the moon for navigationThe lights are like the moon. Perhaps the insects are trying to escape toward the light — or trying to find the dark. Because of an optical illusion called mack bands, Owens said, “the edge of the lighted area will appear darker than the rest of the darkness.”
In 1965, a researcher hypothesized that the lights might be in some way Mimicking mating pheromones. “That was a wild theory!” He said Yash Sundhi, a researcher at the University of Florida studying moths and their sensory systems. “But at that point, not all of the theories had any evidence,” he told Live Science.
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On one level, insects seem to fly to artificial lights because older evolutionary responses are hijacked. “For the vast majority of evolutionary history, night has been almost completely dark,” Owens said.
Specific hypotheses are difficult to test due to the difficulty of observing insects in flight. New technologies may finally bring better answers. in 2023 Prepress on bioRxiv which has yet to be reviewed, Sondhi, along with Samuel Fabian of Imperial College London and other researchers, photographed moths, dragonflies and other insects with a high-speed camera. They noticed something unexpected: moths and dragonflies kept their backs to the light as much as possible.
Based on these observations, the latest theory is that some insects fly to the light as a way to orient themselves: normally, light means up, and dark means down. “It’s hard for them to use gravity to figure out where their body is, because they’re kind of floating through the air,” said Owens, who was not involved in the new research. And with artificial lights, “suddenly, the illuminated half of the universe wasn’t where you’d expect it to be.”
Sondhi and colleagues’ experiment may explain why insects stay near lights once they get there, but not how some insects find lights over long distances or why some stumble and others don’t.
Owens noted that dragonflies kept their backs to the light in the experiment but were not usually found in circular field lights. mites. As for the moths, she said, “there is still a larger question as to why they are there in the first place.” She wants to test the idea that moths use the moon as a compass on a landscape scale, though she said that theory is unfavorable at close range.
Soon, this may be possible thanks to more sensitive cameras and analysis technologies. “The whole field has finally got these tools that we can use to explore these questions,” Owens said.
Meanwhile, Sondi’s findings may support the idea that “excessive lighting” harms insects and should be avoided. “If you put the light on the ground facing up, it will turn upside down and shatter,” Owens said. “We didn’t really notice.”
Sondhi agreed, saying, “Don’t turn the lights up and down.” He also recommended using lights that are more red than blue, given how insects are seen, and turning off outdoor lights whenever possible. “If you turn it off while it’s still dark, many of them will recover and fly off,” Sondy said.
As one light-reducing strategy, Owens suggested finishing summer meals in the dark. “Watch the sunset,” she said, “because the sun sets as fast as your eyes adjust.” “You’ll see really well.” Plus, she added, “If your garden is dark, fewer mosquitoes are likely to find their way there.”
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