July 07, 2017 Posted by: K.A. Holbrook
You could call them Mayflies, Junebugs, dun, shadfly, fishfly or even “Canadian Soldiers”, but the local Hexagonia really is just a nuisance to area residents! The changing ecosystem caused their demise and then also spurred their successful reemergence.  Pollution, climate changes, and agricultural run-off all played a part in Hexagonia’s disappearance in the 1950s. Increased pollution prevention controls and International and National Legislation AND AGREEMENTS OVER WATER QUALITY HAVE IMPROVED OXYGEN LEVELS AND THE WATER QUALITY OF LAKE ERIE.  This in turn has led to the natural return of swarms of Hexagonia.

Mayflies covering utility pole and ground

Eight reasons not to like Mayflies
  1.  They are attracted to lights at night and gather around them in huge numbers.
  2. The decomposing piles give off a fishy stink.
  3. The decomposing Hexagonia serve as a breeding ground for flies.
  4. The streets become slippery with them and can create traffic hazards. When I was young, snow plows were used to clear the Port Clinton Streets of them!
  5. They actually could cause a brownout as they did in 1996 in Northwestern Ohio when swarms settled on a substation.
  6. People are allergic to them and may have asthma-like symptoms and rashes.
  7. They stain your clothes if you sit on them.
  8. They can fly into your mouth or eyes.
Hank uses a leaf blower to remove Mayflies from buildings and walks.Mayflies on a park building

Eight reasons to like Mayflies
  1. Mayflies are an indicator that Lake Erie waters are healthier than they used to be.
  2. They bring diversity to our world.
  3. They are an important source of food for our sport fish and shore birds.
  4. It is a relatively clean and water-loving insect.
  5. The symbolism of their lifecycle speaks of a brief, ephemeral life with meaning.
  6. They are native to Lake Erie and have been here for thousands of years ago.
  7. They can be useful in developing biomedicals, pharmaceuticals and cosmetics.
  8. Their life cycle is AMAZING. The adult “mating dance” in the sky is a beautiful site (look for the Facebook video set to music).
What about this life cycle?
Female Hexagonia actually deposit as many as 8,000 fertilized eggs that sink to the bottom of Lake Erie.  A tiny nymph hatches from each egg in several days to a month.  This nymph life stage is one to two years and it lives in a burrow of sediment at the bottom of the lake. The nymphs feed tiny particles and rely on clean, oxygenated water.   After two years on the bottom, the nymphs begin their ascent.  They may have molted or shed their skins or exoskeletons up to thirty times by the time they reach the surface. Reaching the surface, the mayfly splits its skin and emerges as a fully winged immature adult and flies within minutes. Swarms of Hexagonia leave the lake like synchronized swimmers exiting pool water. Within the next 24 hours, the mayfly undergoes a final molt and is a reproductive adult. The males and females actually mate in darkness in a dance-like flight. Soon the female returns to the lake, depositing her eggs and dies.  The cycle begins again.
This Mayfly has shed its exoskeleton and is now a mature adult.

The exuvier or shed skin is left behind.

Perhaps the BEST response to these unwanted swarms of Hexagonia is to turn your porch light off, sit out under the stars and enjoy the Mayfly dance. Mayflies are truly here today and gone tomorrow. Let’s hope they are back next year as a healthy lake indicator.  Catch my drift?
The Ohio State University Sea Grant Publication “Mayflies and Lake Erie: A sign of the times” by Ken Krieger, Revised 1998 is the primary source of information for this blog.

Great Lakes Restoration Initiative, GLRI, Ranger Kathie, Lake Erie, Mayflies, Mayfly

1 Comments Comments icon

  1. Nancy
    July 08, 2017 at 12:37

    That was such great information, thank you.

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Last updated: July 7, 2017

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