Naturespeak A naturalist's view of the world

June 19, 2010

They’re Baaack!

Filed under: Uncategorized — wykes @ 10:29 pm

Call ‘em Canadian soldiers call ‘em June flies, call ‘em Fishflies – call them what you will, but the Erie shore is currently under attack by hordes of Burrowing Mayflies. The first of several waves has already hit the beaches from the Detroit River mouth and all parts south along the shore to the Ohio line. It happens every year about this time as long warm sunny days melt into humid sultry nights. This daylight/temperature combination stirs the aquatic nymphs of this species into action and incites a mass emergence that can only be categorized as an invasion. Unlike similar invasions of leaf crunching gypsy moths and Japanese beetles, however, this native uprising is a good thing.

I traveled through the Detroit and Woodland Beach neighborhoods – located in northeastern Monroe County – in order to get a feel for this event.  I’d classify this one as “a doozy.” There are few people who actually relish this annual spectacle, but I do. The reason can be stated plainly. Burrowing mayflies spend nearly their entire life in the shallow water environment of the lake and river.  They cannot survive in polluted water and so are considered an indicator species for healthy aquatic environments. In other words: the bigger the hatch, the better the immediate aquatic environment. It’s that simple. For a river and a lake that has experienced a dismal past, this is a significant thing.

Unfortunately, for the human residents of these lakeside communities their view of this event is not that simple. Every house, every tree, every porch light becomes coated with millions of wiggling mayflies. Piles of dead insect bodies accumulate under every streetlight (see below). Passing cars produce a distinctive Rice Krispie sound (snap, crackle, pop!) as their tires flatten trillions of the ill-fated mayflies. Here the speed limit is very low, so the effect is enhanced to the point where you can hear the explosion of every single tiny body. The sound, something akin to popping bubble wrap, was music to my ears but I can certainly see how it could be considered un-nerving to some.

The expression on the face of the young lady I observed spray washing the critters off her car was not one of contented resignation. She was blasting away with a frowning vengeance. A trim white-haired lady crossing the road to get her mail danced her way to and from the box. She was not dancing with joy, but was systematically plucking “flies” off one by one.  Her face was contorted in a way that showed off her well-earned wrinkles. Another pre-teen girl, her smooth face equally contorted, bounced down the road one leg at a time as each appendage was cleared of the unwanted passengers.

I wanted to stop and tell each one of those people the “good news” of the risen flies, but held back. I was the outsider in this affair. I tried to bring up the subject with one fellow but he only returned a disturbing glance and said “you can have them all.” You could tell that he meant what he said.

Burrowing Mayflies, or “Hexs” for short, emerge as winged adults in the evening hours and seek resting spots to pass the daytime hours. In this initial stage they are dark colored sub-imagos. Sometime during the following day they shed their skins one more time and convert to larger yellow imagos. As imagos, they are prime for the big night-time mating flights on the next night. Some will complete the cycle of life and die a happy death, while many others will meet their end beneath rubber Firestone circles. Regardless of the manner, all adult burrowing mayflies die within 48 hours.  Because of this, their invasion waves are intense but short lived.

There was one thing left for me to do before leaving this particular intense invasion site. Upon spotting a small tree which was literally quivering under a mass of mayflies (see video here), I confidently strode up and allowed the mass to transfer to my body.  For a moment, every part of my person was covered and I was happy. Ladies and Gentlemen, this is the face of a man who knows the secret of the mayflies.


  1. WOW! There’s no other word to describe it. WOW! I was just reading about mayfly reproduction in “Six-legged Sex”, but swarms this large were not mentioned. What an incredible experience!

    Comment by Ellen — June 21, 2010 @ 1:35 pm

  2. Don’t the fish just love ’em too?

    Comment by fern — June 22, 2010 @ 9:56 pm

  3. Have you seen them on radar?

    Comment by Minnesotastan — June 26, 2010 @ 11:30 am

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