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The New York Times, In summer 2019, when joking about omens of the apocalypse still seemed fresh and fun, an endless swarm of grasshoppers descended on the Las Vegas Strip.

For weeks, after sunset, their flapping wings filled the Sky Beam shining up from the pyramid of the Luxor casino, and their dead exoskeletons littered the sidewalks. The media speculated the outbreak could be attributed to a wet winter that allowed more eggs to hatch and to the city’s artificial lights, which lured in grasshoppers like moths to flame.

A new analysis substantiates the link to the city’s lights — with worrying implications for the grasshoppers. Elske Tielens, an insect ecologist at the University of Oklahoma, found that on July 26, 2019, the peak night of the invasion, some 46 million grasshoppers took wing and clustered over the brightest parts of the city.

“It’s really hard to wrap your mind around that volume,” she said. “We’re getting more grasshoppers in the air on a single day than you get humans coming to Vegas to gamble across an entire year.”

The glow of Las Vegas’ nighttime wattage escapes straight up into space, where satellites measure it as the brightest city on the planet by a wide margin. The rest of that light, overflowing into the atmosphere, forms a glowing dome that the U.S. National Park Service recently measured from 200 miles away.

Insect ecologists have spent years studying how individual lamps and nighttime traps can be a siren call for insects, tempting them to their deaths. But Tielens and her colleagues, inspired by coverage of the 2019 Vegas grasshopper invasion, saw an opportunity to hunt for a wider pattern. They found the roving clouds of grasshoppers had been visible in weather radar data. Then they overlaid radar movement patterns with maps of the city’s vegetation and its nighttime lighting.

Their study, published this week in Biology Letters, suggested a daily commute. Before dusk, the grasshoppers spread out over a wide area and gathered near vegetation. But as daylight faded, they took to the skies. Then they clustered up to dozens of miles away, traveling not just toward individual bright points, as previous research has shown, but toward the glowiest regions of the Vegas sky.

Brett Seymoure, an ecologist at Washington University in St. Louis, said, “We really don’t have evidence until right now, with this paper, that the light dome is guiding insects.”

Insect ecologists were worried that insect populations were declining around the world, perhaps because of pesticide use, habitat loss, pollution, climate change and artificial light at night. Tielens’ study, Seymoure says, does not estimate how many grasshoppers died, or how the nightly trip into the heart of Vegas might influence the next generation of grasshoppers. But it does show that artificial lighting can influence insects on a regional scale, and that on July 26, 2019, the city’s shimmer summoned 30 metric tons of crunchy, airborne biomass that might otherwise have been spread out across a much larger ecosystem.

— © The New York Times Co.




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