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Mayflies swarm from Missouri River

Posted: 5:18 PM, Jul 09, 2018
Updated: 2018-07-10 07:33:09-04

While we normally use radar to see rain, hail, and wind speeds, it can also pick up on things outside of weather. Such was the case this morning when the National Weather Service in Valley tweeted out a radar loop from between 5 and 5:30 showing swarms of mayflies emerging from the Missouri River.

Glenwood, Iowa fisherman Miles Randolph was impressed by the way the radar caught the swarm.
"That's crazy! That's actually pretty cool. I mean, they may not be when we gotta drive through them, but it is neat to see them actually that bad on the radar."

University of Nebraska Extension Entomologist Jonathan Larson says this is what mayflies do.

"Mayflies are really famous for this mass emergence that they perform. The adults are all timed to come out of the water and molt for the final time and then they are mating," explains Larson.

These small insects live underwater for up to three years of their lives until they emerge from the water to mate.

"So when we see things like this on the weather radar it's just thousands, maybe even millions, of mayflies all together having a big party right before they die. After they mate, they don't last very long," adds Larson.

Although the swarms of mayflies mean the stream or river ecosystem is healthy, fish may not bite as well as all of the mayflies die.

"Could end up with the fish maybe not biting as well because they've got plenty other food sources to eat," says Randolph.

Mayflies are not a harmful insect by nature, but they can create some inconveniences.

"You end up with them all over your clothes, and all over your vehicles. And then they get stuck to you when you go sit in the truck, you gotta pull them out of your seats," adds Randolph.

As interesting of a radar phenomenon as it is, they can also cause some real problems for drivers. A swarm can make seeing through the windshield difficult and they can even cause slick spots on roads after they are crushed.