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Mayfly Watch badge

You can earn this Mayfly Watch badge for reporting a "no" observation followed by a "yes" observation, for either of the two mayfly species, within the same year. See it on your Observation Deck.


Mayflies in the News

Huffington Post takes on mayflies (June 27, 2016)

Our own Mayfly Watch in the news:

Mayfly Watch featured on Director Dan Ashe's blog, Director's Corner (April 15, 2016)

Learn how Mayfly Watch is working with Professor Jerry Kaster of UW-Milwaukee to relocate mayfly eggs to Green Bay (Green Bay Press Gazette, August 14, 2015)

Video: The bane and benefit of mayflies (CBS Evening News with Scott Pelley, July 23, 2015)

Mississippi River mayflies and their lives of excess (Minneapolis StarTribune, July 16, 2015)

Video: Major mayfly emergence expected soon (FWS's Mark Steingraeber explains Mayfly Watch; WXOW 19, July 1, 2015)

Wildlife officials recruit citizen scientists to track Mississippi River phenomenon (LaCrosse Tribune, June 17, 2015)


The graphic above from the National Weather Service NEXRAD Doppler weather radar in La Crosse (WI) illustrates the ebb and flow of the intensity of the reflection of the Doppler radar beam. These reflections are caused by swarms of mayflies as they emerged from the Upper Mississippi River on July 21, 2011. The only reason we know these are mayflies and not another insect is because of observations made by citizen scientists in the area.

Want to go paperless?

Use our mobile apps and skip the paper datasheet. 


iPhone and Android apps available. Make sure you set up your account and sites on a computer before making your mobile observations in the field. 

What is it like to be in a mayfly swarm?

Want to see what it's like to be surrounded by mayflies? Watch this 30 second video, Mayflies on the Mississippi, which was a finalist at the Frozen River Film Festival. 

Watch the 3-minute version for even more swarming! 

Videos produced by USFWS's Dusty Hoffman and Cindy Samples, Upper Mississippi NWFR.

Mayfly Watch

Project Background:

Photo credit: Alan StankevitzEvery year, mayflies emerge from the Mississippi River, and the result can be extraordinary! These insects can swarm by the millions during a large emergence - enough to be picked up by weather radar.

Mayflies are an important food source for fish, especially during the summer emergence but also throughout the year when they are in their larval form. Mayflies are also a public safety hazard when they swarm near lights on roads and bridges, as they can pile up and cause roads to be slick and dangerous for cars. 

The US Fish & Wildlife Service is interested in tracking the timing of seasonal events like these. Our hope is that our neighbors of the river, armed with their mayfly identification, will learn to notice the seasonal changes that occur on the river during the summer.

In the long term, this citizen science-based research will help educate the public that the presence of these insects is an indicator of generally good local water quality conditions during the past year. Information on the predicted timing of emergence can inform managers when to take measrues to ensure the public's safety, such as turning off lights on bridges and encouraging drivers to staff off roads inundated with mayflies.  


We are seeking observers along the Upper Mississippi River to track the timing of the seasonal event of Mayfly emergence. You can join this effort by learning to identify the two species we are tracking and report at the Mayfly Watch phenology monitoring sites or your own location. 

What we're seeing so far...

See predicted mayfly emergence for 2016 and how the real numbers stack up

See predicted mayfly emergence for 2015 and how the real numbers stacked up

See more results from previous years

How to Participate:

1. Join Nature's Notebook. If you haven't already, create a Nature's Notebook account. See our specifics of observing if you need more details on getting started.  

If you have already registered a Nature's Notebook account, go to your Observation Deck, click the link to My Account Details, and add yourself to the Mayfly Watch group (under USFWS -> Region 3). 

2. Set up your Observation Deck. For observations made at one of the Mayfly Watch Pool Sites, be sure you select Mayfly Watch from the dropdown under "Sites" and you will see the sites for the group. If you will be monitoring at one of the Mayfly Watch Pool Sitesview the navigation pool maps to find the pool that is closest to where you live.

For observations made at your own site, set up your own site under My Sites and add one or both of the mayfly species to your site. Follow these instructions on how to create a site and add animals. 

3. Observe mayflies

Report what you see (yes/no/not sure?) for mayflies following the instructions for mayflies or giant mayflies. You should survey the area within 5-10 ft of where you are standing. You may need to walk around the area, inspecting the vegetation along the shoreline for several minutes.

Remember, mayfly abundance may change hourly - you can report multiple observations in one day by reporting the time at which you made the observation. 

We are interested in observations of these two species of mayfly:

Hexagenia bilineata Photo credit: Alan Stankevitz

mayfly, Hexagenia bilineata

Hexagenia limbata Photo credit: Jessica Louque, Smithers Viscient, bugwood.org

giant mayfly, Hexagenia limbata

brown or black yellow

We are interested in the following phenophases for this project. If you observe mayflies, report "yes" to the phenophase that represents the majority of the mayflies you see. 

Phenophase Definition H. bilineata H. limbata
Active adults One or more adults are seen moving about or at rest. Mayfly adults (imagos or "spinners") are brighter in color than subadults, and have clear, glassy wings. (click to enlarge photos)
Active subadults One or more subadults are seen moving about or at rest. Mayfly subadults (subimagos or "duns") are duller in color than adults, and have cloudy wings with a fringe of small hairs. (click to enlarge photos)
Dead adults One or more dead adults are seen, including those found on roads. (click to enlarge photo) Dead adults, Photo: Laura Rettig

Use the Johnson Scale to report the abundance of the mayflies you see: 

Download these instructions


Point of contact:

Erin Posthumus (USA-NPN Liaison to USFWS)