Las Vegas Was Inundated by 46 Million Grasshoppers on a Single Night in 2019

A new study says the horde of insects was drawn to the Vegas Strip by its famously bright lights

Grasshoppers swarm a street light a few blocks from the Las Vegas Strip
Grasshoppers swarm a street light a few blocks from the Las Vegas Strip on July 26, 2019. BRIDGET BENNETT / AFP via Getty Images

One night in the summer of 2019, some 46 million grasshoppers hit the Las Vegas Strip. That total was the peak of a mass insect invasion that besieged the glitzy Nevada city for weeks. A new study used weather radar to estimate the swarm’s size and suggests the bugs were summoned by the city’s famously over-the-top illumination, reports Joshua Sokol for the New York Times.

Vegas landmarks such as the shaft of light emanating from the Luxor pyramid’s pinnacle were especially loaded with the insects, causing many to speculate back in 2019 that the bright lights of the desert city had in fact drawn the insects. The new study, published this week in the journal Biology Letters, confirms those suspicions and manages a rough count of the pallid-winged grasshoppers (Trimerotropis pallidipennis) that made the pilgrimage.

To calculate just how many grasshoppers showed up between June and August in 2019, Elske Tielens, an ecologist at the University of Oklahoma, and her co-authors used weather radar data from the National Oceanic and Atmospheric Administration, reports Susan Milius for Science News.

Looking at the archived weather radar showed roving clouds swirling towards Las Vegas as night fell and lights switched on. After filtering out the regular clouds and other moisture in the air, the researchers could confirm that these clouds were in fact masses of airborne grasshoppers deflecting radar beams normally used to detect storms, according to Science News.

This unorthodox method for counting huge volumes of insects showed that the invasion peaked on July 26, 2019, with approximately 30 metric tons of grasshoppers inundating Las Vegas.

“It’s really hard to wrap your mind around that volume,” Tielens tells the Times. “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 paper is one of the first to show that the glow of a whole city can act as a siren song for insects from far and wide. Light pollution has been shown to negatively impact many species of nocturnal insects and can also disorient birds and even fish.

While the lights of the brightest city in the United States probably won’t be dimming anytime soon, Tielens tells Tom Metcalfe of NBC News, “this knowledge can help researchers both conserve our diverse world of insects, as well as manage important pest species."