In the summer of 2019, when joking about omen of the apocalypse was still fresh and funny, an endless swarm of locusts descended on the Las Vegas Strip.
These insects weren’t biters or harvest killers. But for weeks, every night after sunset, their flapping wings filled the sky beam glowing from the pyramid of the Luxor Casino, and their dead exoskeletons lay on the sidewalks. The news media speculated that the outbreak was due to a damp winter, which allowed more eggs to hatch, and the artificial light in the city that lured locusts to flames like moths.
A new analysis supports the link to the lights of the city – with worrying implications for locusts. Elske Tielens, an insect ecologist at the University of Oklahoma, found that on July 26, 2019, the height of the invasion, around 46 million locusts took wings and then gathered over the brightest parts of the city.
“This tape is really hard to look at,” she said. “We blow up more locusts in a single day than people come to Vegas to play for an entire year.”
The visitors already knew, of course, that Las Vegas increased its performance at night. But some of this light escapes directly into space, where satellites measure it by a large distance as the brightest city in the world. The remainder of this light, which overflows into the atmosphere, forms a glowing dome that the US National Park Service recently measured from a distance of 200 miles in Nevada’s Great Basin National Park.
Insect ecologists have studied for years how individual lamps and night traps can be a silent siren call for insects, seducing them to their death. Dr. However, Tielens and her colleagues, inspired by coverage of the 2019 Vegas locust invasion, saw the opportunity to look for a broader pattern. They found that the wandering grasshopper clouds were also visible on weather radar data. Then they overlaid these radar movement patterns with separate maps of the city’s vegetation and its nighttime lighting.
Their study, published today in Biology Letters, suggested daily commuting. Before dark, the locusts would spread over a large area that gathered near the vegetation. But when the daylight faded, they rose into the sky. Then they gathered tens of kilometers away and moved not only to individual bright points, as previous studies have documented, but also to the brightest regions of the Vegas sky.
“This is a really exciting paper,” said Brett Seymoure, an ecologist at Washington University in St. Louis who did not participate in the research. “We really don’t have any evidence yet that the skylight is guiding insects.”
Insect ecologists were already concerned that various insect populations around the world could decline, possibly due to pesticide use, habitat loss, pollution, climate change and artificial lighting at night. Dr. Tielens’ study, she says, doesn’t estimate how many locusts have died or how the nightly trip to the heart of Vegas could affect the next generation of locusts. However, it shows that artificial light can affect insects on a regional level and that the glimmer of the city on July 26, 2019 conjured up 30 tons of crispy biomass from the air that might otherwise have been spread over a much larger ecosystem.
“It’s scary from an environmental standpoint,” said Dr. Seymoure. “It’s probably pretty terrible for a lot of people in Las Vegas to swarm all these locusts too. Though I think that would be pretty cool to see. “