Apr 15, 2016 I Paul Seaburn

Porch Lights Have Altered the Evolution of Urban Moths

There is no cheaper form of summer entertainment than sitting outside and watching moths fly around a porch light (no, not blitzing into bug-zappers … that’s just cruel). Unfortunately, it appears that this nighttime ritual has affected the evolution of moths. A new study found that porch lights, street lights and other artificial outdoor night lights have permanently altered the behavior of city-dwelling moths and, while it may mean less fried flutterers, it could be bad for the diets of humans. Wait, what? How drunk do you have to be to eat dead moths?

Swiss zoologists Florian Altermatt and Dieter Ebert collected the larvae of ermine moths (Yponomeuta cagnagella) from urban areas with excessive light pollution (Allschwil and Basel City) and from areas with low light pollution (Kleinlützel). They raised 1048 to adulthood in a lab with 16 hours of daylight and 8 hours of darkness daily. Three days after reaching adult mothhood, they were set relatively free in a cage with a fluorescent bulb on the side and observed (great work for unemployed porch light watchers).

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Spindle ermine moth larvae ready for their fifteen minutes of fame

Altermatt and Ebert found that moths from urban moth parents were less attracted to the lights than those whose parents lived in darker areas. According to their recent report in Biology Letters, there was a difference of 30 percent when comparing the flight-to-light behavior of the city and country moths, meaning the city moths stayed away from the lights more. That means more city moths lived longer because bumping into hot porch lights is not healthy behavior.

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Adult spindle ermine moth

How is this evolution of moths bad for human diets? The way urban city moths avoid flying towards porch lights and other nighttime light sources is by not flying at all. This means the moths aren’t doing their jobs.

Moths have jobs? Yep. When they’re not chasing lights, moths are pollinating flowers. With bee populations dropping due to pesticides and pollution, these minor pollinators should have moved up to the major leagues … but this evolutionary change of direction has kept them grounded, meaning less plants and crops that depend on pollination to reproduce.

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A moth at its job site

There’s more. With moths not flying at night, there’s less food for bats, birds and other moth eaters – thus creating a negative ecological chain reaction that will not be good for future generations or animals nor humans.

Something needs to be done. Light pollution is proven to cause problems in humans and animals, disrupt the ecosystem, affect air pollution and make life miserable for astronomers.

Do your part to change moth evolution for the better. Turn off that porch light and talk to your family and neighbors in the dark instead. It’s still cheaper and more entertaining than watching TV. If they ask why, mention the moths and Ray Bradbury’s A Sound of Thunder.

Paul Seaburn

Paul Seaburn is the editor at Mysterious Universe and its most prolific writer. He’s written for TV shows such as "The Tonight Show", "Politically Incorrect" and an award-winning children’s program. He's been published in “The New York Times" and "Huffington Post” and has co-authored numerous collections of trivia, puzzles and humor. His “What in the World!” podcast is a fun look at the latest weird and paranormal news, strange sports stories and odd trivia. Paul likes to add a bit of humor to each MU post he crafts. After all, the mysterious doesn't always have to be serious.

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