Massive Mayfly Hatch of "Biblical Proportions" Triggers a Three-Car Crash

Massive Mayfly Hatch of "Biblical Proportions" Triggers a Three-Car Crash
La Crosse, July 20, 2014. Courtesy of the National Weather Service

A massive mayfly hatch on the Mississippi River in the La Crosse, Wisconsin area July 20, 2014, was described as a insect infestation of "biblical proportions" so intense that it made driving in the region difficult and even dangerous. Poor visibility and slippery roads (due to mayflies) were blamed for a three-vehicle accident on the Hwy. 63 bridge linking Red Wing and Hager City, Wisconsin, that left one person hospitalized.

The hatch captured on the National Weather Service's (NWS) Doppler radar looks like a rain storm, but is actually a cloud of Hexagenia bilineata mayflies stretching from Redwing Minnesota in the north to to Prairie du Chien Wisconsin.

National Weather Service radar image July 20, 2014

According to the NWS: "The radar detected the flies about 8:45 pm, emanating from the river (the source) with echo values similar to that of light-moderate rain (35-40 dBZ). With a general south-to-north wind flow above the surface, the mayflies quickly moved north once in the air. As the flies dispersed moving north-northeast, they also gained altitude with some of the echo being detected as far north as Black River Falls and as high as 2,500 feet above ground.

"By late evening, mayflies were swarming in La Crosse, La Crescent, Stoddard and points up and down the river. While the emergence of mayflies from their river bottom mud dwelling can occur at various times through the warm season depending on the species, this particular emergence was that of the larger black/brown bilineata species. The radar loop shows the reflected radar energy (reflectivity) from 835 pm to just after midnight. The higher the values (greens to yellows) indicate greater concentrations of flies."


Last year along the Mississippi, similar but less intense hatches of the same species occurred on June 15, 18 and 25, and on July 14.


June 23, 2012 was the last hatch of this size. That event was also termed "massive" by the NWS, and it too caused collisions and required snowplows for cleanup duty.


According to the NWS, the heavy hatches in recent years are the result of environmental protections that are resulting in cleaner water and better habitat for the burrowing mayflies.

//www.flyfisherman.com/files/2014/07/MinnesotaCity.jpg
Minnesota City, July 20, 2014. Courtesy of the National Weather Service.
//www.flyfisherman.com/files/2014/07/timh1.jpg
La Crosse, July 20, 2014. Courtesy of the National Weather Service
//www.flyfisherman.com/files/2014/07/TrempGasStation.jpg
Trempealeau, July 20, 2014. Courtesy of the National Weather Service.
//www.flyfisherman.com/files/2014/07/fliesWindow.jpg
La Crosse, July 20, 2014. Courtesy of the National Weather Service.

http://youtu.be/BkLV8zWiRVk

Get Your Fish On.

Plan your next fishing and boating adventure here.

Recommended for You

Here's a look at 8 new fly lines for 2019. Lines

8 New Fly Lines for 2019

Fly-Fisherman

Here's a look at 8 new fly lines for 2019.

The Kamikaze Sculpin is easy to tie, versatile, and smartly designed to get the job done. Fly Tying

Tying the Kamikaze Sculpin

Charlie Craven

The Kamikaze Sculpin is easy to tie, versatile, and smartly designed to get the job done.

Modern methods for catching smallmouths on topwater flies. Bass

How to Catch Smallmouth Bass on Topwater Flies

Dave Karczynski and Tim Landwehr

Modern methods for catching smallmouths on topwater flies.

See More Recommendations

Popular Videos

Black Beauty

Black Beauty

Master fly tier Charlie Craven discuss the tools and materials needed to tie the Black Beauty.

Bahamas - Bonefish

Bahamas - Bonefish

Conway casts for his personal best bonefish while fishing the Grand Bahama islands.

 Getting Started In Fly Fishing

Getting Started In Fly Fishing

Getting Started In Fly Fishing

See more Popular Videos

Trending Stories

As you explore your home water, keep in mind what they are are eating to select the best carp flies! Flies

The 15 Best Carp Flies

Jay Zimmerman - September 27, 2016

As you explore your home water, keep in mind what they are are eating to select the best carp...

Drift boats help you search through miles of river quickly and effectively. Here's the top models on the market today. Gear

Top Drift Boats of 2019

John Fedorka - April 02, 2019

Drift boats help you search through miles of river quickly and effectively. Here's the top...

George Daniels offers his advice on which types of fly-fishing leaders are best for the most common applications you'll encounter on the water. How-To

Picking the Perfect Fly-Fishing Leader

George Daniel - January 22, 2018

George Daniels offers his advice on which types of fly-fishing leaders are best for the most...

See More Stories

More Industry

The U.S. National Fly Fishing Championships are slated to be held May 30th through June 2nd, and this year's host city will be Bend, Oregon. Industry

U.S. National Fly Fishing Championships

Jonathan Wright - May 09, 2018

The U.S. National Fly Fishing Championships are slated to be held May 30th through June 2nd,...

It began with love of a river that he fished as a boy with his father, and a passion for the sport that still endures today. Industry

Abe's Fly Shop Turns 60

Jay Walden - February 22, 2019

It began with love of a river that he fished as a boy with his father, and a passion for the...

Imperiled Yellowstone Cutthroat Trout are getting a helping hand with new strategies being developed by fisheries managers to control invasive predators. Industry

Yellowstone Cutthroat Trout Get New Help

Jonathan Wright - May 18, 2018

Imperiled Yellowstone Cutthroat Trout are getting a helping hand with new strategies being...

See More Industry

GET THE MAGAZINE Subscribe & Save

Temporary Price Reduction.

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW THIS MONTH'S ISSUE

GET THE NEWSLETTER Join the List and Never Miss a Thing.

×