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“Mayfly Numbers Drop By Half Since 2012, Threatening Food Chain”

“Mayflies, which form swarms in the billions that are visible on weather radar, are in steep decline, mirroring the plight of insects worldwide.”

“Every summer, mayflies burst forth from lakes and rivers, taking to the skies of North America. These insects, which are particularly abundant in the northern Mississippi River Basin and Great Lakes, live in the water as nymphs before transforming into flying adults. They synchronize their emergence to form huge swarms of up to 80 billion individuals—so massive that, in waterside towns, they are sometimes scooped up with snowplows.

These insect explosions provide food for a wide variety of animals, from perch and other commercially important freshwater fish to birds and bats. But new research shows that mayflies are in decline. Since 2012, mayfly populations have declined by more than 50 percent throughout the northern Mississippi and Lake Erie, likely due to pollution and algal blooms, according to a study published today in Proceedings of the National Academy of Sciences.

“We were really surprised to see that there was a decline year after year,” says lead author Phillip Stepanian, a bio-meteorologist at the University of Notre Dame. “That was really unexpected.””

Douglas Main reports for National Geographic January 20, 2020.