Mayfly hatch is a sure sign of summer

RED WING, MINN. – A slimy windshield? Check. Bug carnage along the riverbanks? Check.

Delicately winged insects fixed to light poles, light bulbs, headlights, signs, tree trunks, and just about anything standing near the river, including a hiker who goes motionless for a few moments? Check, check, check, and (yeeesh!) check.

A hike along the Mississippi here this weekend means coming face-to-bug-eyed-face with the mayfly hatch, a marvel of the natural world regarded as commonplace in Minnesota rivertowns.

This year's hatches up and down the river haven't produced record-busting piles of bug corpses as they do some years or required the help of snowplows to clear bridges and waterfront highways — not an urban myth, it's actually happened — but it's still remarkable to note that mayflies have made their annual return.

"It doesn't look like it's huge this year," said Gary Montz, a research scientist with the Department of Natural Resources. "Some people will say 'What a nuisance,' but if you have a lot of mayflies, it's a good thing for the aquatic system."

The bugs most people see are just the final, very brief stage of a life cycle that begins on river and lake bottoms, said Montz.

The burrowing mayfly common along the Mississippi builds a hole in the river bottom and lives most of its life there, usually emerging en masse in late spring and summer to mate, lay eggs, and die in a frantic swarm that lasts a day or two. They need oxygenated water and a healthy river to survive their larval stage, so their emergence should be taken as a sign that the river's in good shape, said Montz.

Like the first snowfall of winter, the hatch is a hard-to-miss marker of a season's arrival in places like Red Wing, Hastings, Stillwater and Marine-On-St.-Croix. This year in Hastings, it even inspired a new beer.

Spiral Brewery co-owner Amy Fox said her company's limited edition Maibock, called "the Hatch," went as quickly as the swarms of bugs. The cans of the deep golden beer with a strong malty and lightly toasted aroma are already sold out, though the Hatch is still available at the brewery's taproom.

Seeing the mayflies emerge each year was just part of growing up along the Mississippi, she said.

"You're used to it, living on the river," said Fox. "The lights are off and you just kind of wait for them to come."

Fishing can be better during a hatch, at least at first, said river fishing guide Jeremiah Luhmann of Luhmann's River Guiding.

"It turns the fish on, but they get full pretty fast and slow the fishing down a bit," he said.

The hatch this year seems about average, Luhmann said, though he heard from a buddy near Harpers Ferry, Iowa, that the hatch there was much larger.

And a June hatch near La Crosse, Wis., was so enormous it registered on local weather radar as tiny dots swirling above the city.

Even during this year's smaller hatches in Hastings, the city turned off bridge lights and some city lights to prevent pileups, said city spokeswoman Lee Stoffel. The public works crew gets the job of cleaning up in bigger years, she added.

"It doesn't compare to some of the worst we've seen," said Hastings Public Works Director Nick Egger.

A few years ago, parks crews used leaf blowers to clean up after the hatch, but this year has been more manageable, he said.

"Frankly," Egger said, "you can't get them all."

@_mattmckinney • 612-673-7329