When Do Mayflies Hatch: Insight into Their Life Cycle

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Mayflies are fascinating insects, known for their unique life cycle and unmistakable presence near water sources. There’s a specific time of year when they hatch, and if you’re curious about when this happens, you’re in the right place.

Mayfly eggs typically hatch within minutes, days, or weeks after being laid, depending on the species and environmental conditions source. These delicate creatures emerge from the water, often around dawn or dusk, in massive numbers and fill the air above rivers and lakes source.

It’s essential to understand the mayfly’s hatching period, as their presence indicates the health of the water’s ecosystem. So, as you witness their synchronous dance, you’re also seeing firsthand the natural balance of the environment at work.

Understanding Mayflies

Basic Characteristics

Mayflies are delicate, soft-bodied insects with large compound eyes and short antennae. Their wings are membranous and held upright, resembling a butterfly’s posture. Some interesting features of mayflies include:

  • Slender body
  • Four veined wings
  • Two long, threadlike cerci at the tip of the abdomen
  • Front pair of legs often held outward when perching

Lifecycle and Stages

Mayflies have a unique and relatively short lifecycle. Their metamorphic cycle includes an uncommon subimago stage between the larval and adult stages. The stages in their life cycle are:

  1. Egg
  2. Larva (Nymph)
  3. Subimago (pre-adult)
  4. Imago (adult)

Mayfly larvae develop in aquatic environments and are sensitive to pollution, making them good indicators of water quality. Once they molt into the subimago stage, they emerge from the water and begin to fly. The final molt into the adult stage takes place soon after, and they only live for a short period, typically just a few days.

Mayfly Species

There are numerous species of mayflies worldwide, with varying habitats and characteristics. The Siphlonurus autumnalis is a noteworthy example of a mayfly species with a restricted distribution and low population size. Some common families of mayflies in North America can be found here.

Ephemeroptera Order

Mayflies belong to the Ephemeroptera order, which is known for its diversity and distribution, as well as their short adult lifespan. These insects play important ecological roles in aquatic ecosystems and are often referred to as “up-winged flies” due to their wing posture. By understanding the basic characteristics, lifecycle, and different species within the Ephemeroptera order, you can appreciate the role of mayflies in the natural world.

Hatching of Mayflies

Hatching Process

Mayflies undergo a unique metamorphic cycle, which includes a subimago stage between the ultimate larval instar and the mature adult stage (or imago) source. During their hatching, mayflies emerge from the water, often at dawn or dusk source.

These fragile insects can form dense clouds while dancing above the water surface. Copulation happens quickly, and females lay their eggs either singly or in clusters.

Timing and Climate Factors

Typically, Mayflies hatch in the summer months, with the peak emergence occurring around July source. The timing of their hatching depends on various climate factors, such as temperature and humidity.

For example:

  • Warmer climates may cause an earlier hatch
  • Cooler climates may delay the hatch

Role of Water Quality

Water quality plays a significant role in the hatching and survival of mayflies. They require clean water for their development and can serve as indicators of water qualitysource.

The presence of mayflies in an aquatic ecosystem suggests good water quality. Conversely, their absence can indicate water pollution or poor water quality.

In summary, the hatching of mayflies involves a unique metamorphic cycle, and their emergence is influenced by timing, climate factors, and water quality.

Mayflies and Ecosystem

Diet and Predation

Mayflies, specifically in their subimago stage, are a crucial part of the food chain. They serve as a diet to various birds and fish species, particularly trout. These insects are essential for maintaining a healthy balance in both freshwater and terrestrial ecosystems. For instance, the presence of mayflies in a body of water often indicates a good water quality and a stable fish population.

Environmental Implications

Their presence could also be an indicator of environmental health. When mayflies are in abundance, it usually denotes a lack of pollution in the area. They are sensitive to water quality, meaning that they thrive in clean water with well-oxygenated conditions. The absence of these insects in an ecosystem may suggest environmental disturbances, such as pollution or changes in water flow patterns.

Ecological Significance

Mayflies play a distinct role in their respective habitats. Their consumption of algae, for example, helps regulate the growth of these simple plants, preventing algal blooms that could otherwise harm the ecosystem. In addition, when mayflies die, they decompose and become organic matter, enriching the nutrients in the environment.

To summarize, mayflies have a unique ecological significance, directly and indirectly impacting various aspects of the environment. They provide insight into water conditions and contribute to ecosystem health through predation, regulation of algae growth, and enrichment of nutrients.

Mayfly Behavior and Survival Strategies

Swarms and Mating Rituals

Mayflies exhibit fascinating behaviors, with one of the most notable being their swarming and mating rituals. The adult stage, also known as the imago, is primarily focused on mating. During this process, mayflies gather in large swarms that can consist of thousands of individuals. Males perform aerial dances to attract females, who then join the swarm to mate.

The winged duns, or subimagos, also participate in these mating rituals. Their unique life stage allows them to grow wings and prepare for the final molt into the adult form. Once mating is complete, females deposit their eggs in water, where nymphs will hatch and begin their underwater life.

Defense Mechanisms

Mayflies have a few defense mechanisms to help them survive, such as:

  • Camouflage: The coloration of nymphs often matches their surroundings, helping them blend in and avoid predators.
  • Escape behaviors: Some nymphs display rapid, dart-like swimming motions to evade predators.
  • Body flattening: Nymphs of certain species can flatten their bodies against surfaces, making them difficult to detect in their underwater habitats.

Mayfly Swarming on Weather Radar

Incredibly, mayfly swarms can be so dense, they sometimes appear on weather radar! While this phenomenon is not typical, it provides a glimpse into the sheer numbers of these insects when they congregate.

To minimize the ecological light pollution, which may impact mayfly behavior, experts suggest maintaining and increasing the proportion of naturally illuminated areas. By doing so, mayflies can continue their age-old survival strategies and thrive in their natural habitats.

Mayflies and Fly Fishing

Significance for Fly Fishermen

Mayflies play a crucial role in the sport of fly fishing. Their emergence from the water provides an abundant food source for trout and other fish, making it a prime time for fly fishermen to cast their lines. When mayflies hatch, they go through two primary stages: the dun and imago, or spinner stage. Both stages are important for fly fishermen, as they offer opportunities to mimic the insects and entice the fish to bite their artificial flies.

During a mayfly hatch, fish will be more active and selective in their feeding, so it’s essential to match your fly to the hatch. Hatches on southeast Minnesota trout streams generally occur within a specific time frame, but some streams may have unique hatches not listed.

Imitating Mayflies in Fly Fishing

Matching the hatch isn’t only about size and color; it’s also about the stage of development. Some examples of artificial flies used to mimic mayflies include:

  • Dry flies for dun stage: These flies are designed to float on the surface, imitating the mayfly duns as they emerge from the water.
  • Wet flies for spinner stage: These flies are designed to imitate the spent spinners, or adult mayflies that come into their final stage before laying eggs and dying.

When choosing a fly, consider the following features:

  • Size: Mayflies can vary significantly in size. Pick a fly that is similar in size to the natural insects.
  • Color: Pay attention to the color of the natural mayflies and choose a fly that matches it.
  • Shape: Different species of mayflies have distinct shapes. Choose a fly that resembles the natural insects.

Fly Fishing Techniques

Catching fish during a mayfly hatch can be challenging but rewarding. Here are some techniques to increase your chances:

  • Observe: Study the water, noting the mayflies’ activity and the fish feeding on them. Use this information to inform your fly and fishing techniques.
  • Presentation: Cast your fly to drift naturally with the current, keeping your line and leader as far from the fish as possible to avoid detection.
  • Patience: Fish can be selective during a hatch. Be prepared to change flies, adjust your technique, and persevere until you find what works best.

Remember, practice makes perfect. Enjoy the challenge and thrill of fly fishing during a mayfly hatch, and you’ll be rewarded with an unforgettable experience.

Historical and Cultural Significance

Mayflies in Literature

In the world of literature, mayflies have inspired various writers and poets. For instance, the Greek philosopher Aristotle dedicated a section of his work History of Animals to mayflies, examining their short lifespans. Another famous poet, George Crabbe, mentioned mayflies in his poem The Borough, highlighting them as a symbol of life’s fleeting nature.

Historical Accounts and Anecdotes

Throughout history, mayflies have found their way into various anecdotes and accounts. One notable story involves Canadian soldiers during World War II. At times, swarms of mayflies became so dense that the soldiers believed they were under enemy fire. These insects were even given the nickname “Canadian Soldiers” due to their brief yet noticeable presence, similar to the short lifespan of mayflies.

Mayflies Around The World

Mayflies are found in numerous countries around the globe. In Canada, mayflies are celebrated as a sign of clean waterways and a healthy ecosystem, despite the inconvenience they may sometimes cause. In Malawi, the annual hatching of mayflies is known as the “lake fly hatch“, and it draws millions of swarming insects to the shores of Lake Malawi. This event is even considered a tourist attraction, as people come to witness the remarkable sight.

  • Aristotle: Examined mayflies’ short lifespans in History of Animals
  • George Crabbe: Mentioned mayflies in his poem The Borough
  • Canadian soldiers: Mayflies nicknamed “Canadian Soldiers” during World War II
  • Canada: Mayflies signifying clean waterways and a healthy ecosystem
  • Malawi: Annual lake fly hatch in Lake Malawi as a tourist attraction

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Mayflies

 

What are these?!
Location: South Carolina
June 19, 2011 2:42 pm
My daughter and I found these on our back porch in SC in the summertime. We found three yellow ones and one brown one…
Signature: Rebekah

Giant Mayfly subimago

Dear Rebekah,
All of your photos are of Mayflies in the order Ephemeroptera, and we believe they are Giant Mayflies, or Golden Mayflies, or Burrowing Mayflies in the genus
Hexagenia, based on images posted to BugGuideBugGuide notes:  “Very large mayflies. Usually pale golden yellow at least when freshly emerged, i.e., subimago. Several species dark with bold striped pattern as mature imagos. Wings not uniformly dark, as are some other genera of this family. Pale brown band across abdomen. Antennae, legs, and tails yellow. (Photographs show either pale golden mayflies–probably subimagos, or very dark individuals, full imagoes?)”  Mayflies are unique among insects in that they molt twice as adults.  Daniel Marlos in his book, The Curious World of Bugs, writes:  “Shortly after emerging from the water in preparation for becoming an adult, the naiad, or aquatic nymph, molts and assumes its winged form.  This is known as the subimago because within a few hours, it will molt again, shedding even the covering of its wings, at which point it becomes a full adult, or imago.”  We are inclined to believe that your yellow individuals are sumimagos, and the brown individual is an imago or mature adult.

Giant Mayfly imago

Letter 2 – Male Spring Fishfly

 

Subject: Possible caddisfly?
Location: Lewis Center, OH
May 26, 2016 2:03 pm
Hi I found this guy today (May 26th 2016) on the screen door of my house. I thought it was a caddisfly, but those feathered antenna! He also looks like he has yellow fangs.
Signature: JRH

Male Spring Fishfly
Male Spring Fishfly

Dear JRH,
This is a male Fishfly, most likely a Spring Fishfly,
Chauliodes rastricornis, a species pictured on BugGuide where it states they are found “Near calm bodies of water with detritus.”

Letter 3 – Male Spring Fishfly

 

Subject: It has 2 centimeter black things on its head and wings
Location: Clinton, CT
May 29, 2016 5:29 pm
Dear bugman please let me know what this bug is
Signature: Ross

Male Spring Fishfly
Male Spring Fishfly

Dear Ross,
This is a male Spring Fishfly, Chauliodes rastricornis, and according to BugGuide:  “The comb-like, (pectinate) antennae of the males are quite obvious” while “The antennae of females are serrate (saw-like).”  BugGuide also notes:  “Adults typically fly late spring: March?-May (North Carolina), April-May (West Virginia). Seen into early June in New England (Massachusetts–guide photo). Further south, much of year (Florida).”  This individual seems right on time for your part of New England.

Letter 4 – Male Spring Fishfly

 

Subject: never seen before bug
Location: Laval North west subburbs, Quebec
June 20, 2016 5:45 am
Hello Here is a photo of a winged insect that is very beautiful but we never seen any of them before.
Signature: Richard

Male Spring Fishfly
Male Spring Fishfly

Dear Richard,
This is a male Spring Fishfly,
Chauliodes rastricornis, which you can verify by comparing to this BugGuide image.  According to BugGuide:  “The antennae of females are serrate (saw-like):  The comb-like, (pectinate) antennae of the males are quite obvious.”  BugGuide data indicates Quebec sightings occur in June and July.

Thank you
I and will go to sleep a little smarter.
Love that guide will start using it more and more
Site is a bit intimidating with its large content I will get familiar.
Is there a way to arrive at an identification beside looking at all the items ? like a series of questions that would narrow the search?
Thanks again
Richard

The search engine on our site might be helpful if you type in a few key words.  Because people send in letters that we post verbatim, there is pop culture language on the site that is used to describe the insects.  Prior to the advent of cellular telephones with cameras and internet connectivity, the letters were a bit wordier because they were typed on a computer.  We just typed in “beautiful winged insect” and your posting came up early, but Giant Conifer Aphids also came up, but not because they were described as beautiful, but because the tree they were living on was described as “beautiful and expensive.”

Letter 5 – Male Spring Fishfly

 

Subject:  What’s that bug?
Geographic location of the bug:  Tampa, Florida
Date: 01/23/2018
Time: 10:17 PM EDT
Your letter to the bugman:  I found this bug on the outside wall of my garage. Snapped this photo with my phone.  Very interested in finding out what it is!  Thank you
How you want your letter signed:  Selcuk Mumcu

Hey – we found it.  It was a FISHFLY….

Male Spring Fishfly

Dear Selcuk,
You are correct.  We believe this is a male Spring Fishfly, which is pictured on BugGuide.

Letter 6 – Male Summer Fishfly

 

Subject: What is this scary thing?
Location: West cape may
July 30, 2016 10:44 am
This picture was taken in west cape may today.
Signature: Lynda

Male Summer Fishfly
Male Summer Fishfly

Dear Lynda,
This looks like a harmless male Summer Fishfly to us.

Letter 7 – Mayflies and more Mayflies, including a Mayfly being eaten by a Jumping Spider

 

may fly pics
Location:  south western ontario
August 4, 2010 11:48 am
thought you may want to share some good pics of mayflys
bug-eyed canadian

Mayfly

Dear bug-eyed canadian,
We are very happy to get your excellent images of Mayflies.

Mayfly

Mayflies constitute an important component of the food chain, especially when they appear in prodigious numbers.  They feed fish, birds, other insects, and spiders including Jumping Spiders like the one in your Food Chain image.

Jumping Spider eats Mayfly

Letter 8 – Mayflies attracted to porch light in Whittier

 

small fly with forked tail
Location: California, Whittier (Los Angeles suburban)
July 2, 2011 10:02 pm
We recently have a large number of these flies on our porch. They don’t move around much and cling to the stucco wall. We have about 50 of them in a small area. Do you know what they are ? Are they a sign of a problem with the house (like a termite infestation or similar) ?
Signature: Dave

Mayfly

Hi Dave,
You have Mayflies, the winged adult of an aquatic naiad, congregating around your porch light.  There must be a nearby pond or stream that is providing the habitat for the nymphs.  Though fifty individuals may seem like a swarm, in places in the midwest, millions of Mayflies are attracted to street lights and the pavement can become slick with their crushed bodies.  See this posting from our archives.  Mayflies do not feed as adults, and they only live long enough to mate and reproduce, and possibly provide a food source for the many predators that feed upon insects.  They tend to be more common in the spring, hence the name Mayfly, but they can be found at other times as well.

Mayflies at the porch light

Letter 9 – Mayflies en masse

 

Mayflies in………May (imagine that)
May 6, 2010
These bad boys have been covering the walls outside my garage every night for the last 3 nights (it’s May 6th) and in the morning all but a few are dead. I have to get the leaf blower out to clear them out. The cat seems to enjoy playing with them though.
Jeff in the Panhandle of FL.
Baker, FL.

Mayflies

Hi Jeff,
YOur photo is really stunning.  We have read that Mayflies can get so numerous in the Great Lakes region that when they are attracted to street lights and fall to the ground, the pavement is slippery with their squashed bodies.  When Mayflies swarm, they are a very important food source for fish and other wildlife.  We are setting your letter to post in our absence on Monday, and it will be the only letter that posts that day.

Mayflies

Letter 10 – Mayfly

 

More unidentified critters
I photographed three of these on recent trips to Arkansas and one at a local park here in Southern Cal. Hoping you could help me identify them.
Thanks
Rus

Hi Rus,
This Mayfly is one of your Arkansas critters. Mayflies belong to the Order Ephemeroptera which alludes to the fact that they only live a day, though some live several days. May is not the only month they are found. When they emerge as adults, they usually do so in great numbers. Their nymphs or naiads are aquatic. Your photo is stunning, and will result in a new page for our site.

Identification Update:
(08/01/2005) The mayfly is a male subimago of the genus Hexagenia. The nymphs are burrowers in mud and debris in clean streams and rivers. This one is related to the mayflies that occasionally form huge emergence swarms on the upper Mississippi and the Great Lakes. Hope this helps.
Sincerely,
R. Wills Flowers
Center for Biological Control
Florida A&M University
Tallahassee, FL 32307

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Mayflies

 

What are these?!
Location: South Carolina
June 19, 2011 2:42 pm
My daughter and I found these on our back porch in SC in the summertime. We found three yellow ones and one brown one…
Signature: Rebekah

Giant Mayfly subimago

Dear Rebekah,
All of your photos are of Mayflies in the order Ephemeroptera, and we believe they are Giant Mayflies, or Golden Mayflies, or Burrowing Mayflies in the genus
Hexagenia, based on images posted to BugGuideBugGuide notes:  “Very large mayflies. Usually pale golden yellow at least when freshly emerged, i.e., subimago. Several species dark with bold striped pattern as mature imagos. Wings not uniformly dark, as are some other genera of this family. Pale brown band across abdomen. Antennae, legs, and tails yellow. (Photographs show either pale golden mayflies–probably subimagos, or very dark individuals, full imagoes?)”  Mayflies are unique among insects in that they molt twice as adults.  Daniel Marlos in his book, The Curious World of Bugs, writes:  “Shortly after emerging from the water in preparation for becoming an adult, the naiad, or aquatic nymph, molts and assumes its winged form.  This is known as the subimago because within a few hours, it will molt again, shedding even the covering of its wings, at which point it becomes a full adult, or imago.”  We are inclined to believe that your yellow individuals are sumimagos, and the brown individual is an imago or mature adult.

Giant Mayfly imago

Letter 2 – Male Spring Fishfly

 

Subject: Possible caddisfly?
Location: Lewis Center, OH
May 26, 2016 2:03 pm
Hi I found this guy today (May 26th 2016) on the screen door of my house. I thought it was a caddisfly, but those feathered antenna! He also looks like he has yellow fangs.
Signature: JRH

Male Spring Fishfly
Male Spring Fishfly

Dear JRH,
This is a male Fishfly, most likely a Spring Fishfly,
Chauliodes rastricornis, a species pictured on BugGuide where it states they are found “Near calm bodies of water with detritus.”

Letter 3 – Male Spring Fishfly

 

Subject: It has 2 centimeter black things on its head and wings
Location: Clinton, CT
May 29, 2016 5:29 pm
Dear bugman please let me know what this bug is
Signature: Ross

Male Spring Fishfly
Male Spring Fishfly

Dear Ross,
This is a male Spring Fishfly, Chauliodes rastricornis, and according to BugGuide:  “The comb-like, (pectinate) antennae of the males are quite obvious” while “The antennae of females are serrate (saw-like).”  BugGuide also notes:  “Adults typically fly late spring: March?-May (North Carolina), April-May (West Virginia). Seen into early June in New England (Massachusetts–guide photo). Further south, much of year (Florida).”  This individual seems right on time for your part of New England.

Letter 4 – Male Spring Fishfly

 

Subject: never seen before bug
Location: Laval North west subburbs, Quebec
June 20, 2016 5:45 am
Hello Here is a photo of a winged insect that is very beautiful but we never seen any of them before.
Signature: Richard

Male Spring Fishfly
Male Spring Fishfly

Dear Richard,
This is a male Spring Fishfly,
Chauliodes rastricornis, which you can verify by comparing to this BugGuide image.  According to BugGuide:  “The antennae of females are serrate (saw-like):  The comb-like, (pectinate) antennae of the males are quite obvious.”  BugGuide data indicates Quebec sightings occur in June and July.

Thank you
I and will go to sleep a little smarter.
Love that guide will start using it more and more
Site is a bit intimidating with its large content I will get familiar.
Is there a way to arrive at an identification beside looking at all the items ? like a series of questions that would narrow the search?
Thanks again
Richard

The search engine on our site might be helpful if you type in a few key words.  Because people send in letters that we post verbatim, there is pop culture language on the site that is used to describe the insects.  Prior to the advent of cellular telephones with cameras and internet connectivity, the letters were a bit wordier because they were typed on a computer.  We just typed in “beautiful winged insect” and your posting came up early, but Giant Conifer Aphids also came up, but not because they were described as beautiful, but because the tree they were living on was described as “beautiful and expensive.”

Letter 5 – Male Spring Fishfly

 

Subject:  What’s that bug?
Geographic location of the bug:  Tampa, Florida
Date: 01/23/2018
Time: 10:17 PM EDT
Your letter to the bugman:  I found this bug on the outside wall of my garage. Snapped this photo with my phone.  Very interested in finding out what it is!  Thank you
How you want your letter signed:  Selcuk Mumcu

Hey – we found it.  It was a FISHFLY….

Male Spring Fishfly

Dear Selcuk,
You are correct.  We believe this is a male Spring Fishfly, which is pictured on BugGuide.

Letter 6 – Male Summer Fishfly

 

Subject: What is this scary thing?
Location: West cape may
July 30, 2016 10:44 am
This picture was taken in west cape may today.
Signature: Lynda

Male Summer Fishfly
Male Summer Fishfly

Dear Lynda,
This looks like a harmless male Summer Fishfly to us.

Letter 7 – Mayflies and more Mayflies, including a Mayfly being eaten by a Jumping Spider

 

may fly pics
Location:  south western ontario
August 4, 2010 11:48 am
thought you may want to share some good pics of mayflys
bug-eyed canadian

Mayfly

Dear bug-eyed canadian,
We are very happy to get your excellent images of Mayflies.

Mayfly

Mayflies constitute an important component of the food chain, especially when they appear in prodigious numbers.  They feed fish, birds, other insects, and spiders including Jumping Spiders like the one in your Food Chain image.

Jumping Spider eats Mayfly

Letter 8 – Mayflies attracted to porch light in Whittier

 

small fly with forked tail
Location: California, Whittier (Los Angeles suburban)
July 2, 2011 10:02 pm
We recently have a large number of these flies on our porch. They don’t move around much and cling to the stucco wall. We have about 50 of them in a small area. Do you know what they are ? Are they a sign of a problem with the house (like a termite infestation or similar) ?
Signature: Dave

Mayfly

Hi Dave,
You have Mayflies, the winged adult of an aquatic naiad, congregating around your porch light.  There must be a nearby pond or stream that is providing the habitat for the nymphs.  Though fifty individuals may seem like a swarm, in places in the midwest, millions of Mayflies are attracted to street lights and the pavement can become slick with their crushed bodies.  See this posting from our archives.  Mayflies do not feed as adults, and they only live long enough to mate and reproduce, and possibly provide a food source for the many predators that feed upon insects.  They tend to be more common in the spring, hence the name Mayfly, but they can be found at other times as well.

Mayflies at the porch light

Letter 9 – Mayflies en masse

 

Mayflies in………May (imagine that)
May 6, 2010
These bad boys have been covering the walls outside my garage every night for the last 3 nights (it’s May 6th) and in the morning all but a few are dead. I have to get the leaf blower out to clear them out. The cat seems to enjoy playing with them though.
Jeff in the Panhandle of FL.
Baker, FL.

Mayflies

Hi Jeff,
YOur photo is really stunning.  We have read that Mayflies can get so numerous in the Great Lakes region that when they are attracted to street lights and fall to the ground, the pavement is slippery with their squashed bodies.  When Mayflies swarm, they are a very important food source for fish and other wildlife.  We are setting your letter to post in our absence on Monday, and it will be the only letter that posts that day.

Mayflies

Letter 10 – Mayfly

 

More unidentified critters
I photographed three of these on recent trips to Arkansas and one at a local park here in Southern Cal. Hoping you could help me identify them.
Thanks
Rus

Hi Rus,
This Mayfly is one of your Arkansas critters. Mayflies belong to the Order Ephemeroptera which alludes to the fact that they only live a day, though some live several days. May is not the only month they are found. When they emerge as adults, they usually do so in great numbers. Their nymphs or naiads are aquatic. Your photo is stunning, and will result in a new page for our site.

Identification Update:
(08/01/2005) The mayfly is a male subimago of the genus Hexagenia. The nymphs are burrowers in mud and debris in clean streams and rivers. This one is related to the mayflies that occasionally form huge emergence swarms on the upper Mississippi and the Great Lakes. Hope this helps.
Sincerely,
R. Wills Flowers
Center for Biological Control
Florida A&M University
Tallahassee, FL 32307

Authors

  • Bugman

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

    View all posts
  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

    View all posts
Tags: Mayfly

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4 Comments. Leave new

  • Hehe, I remember a family camping trip up around one of the lakes. During the night I got up to use the campground’s bathroom. I didn’t use a flashlight. There was kind of a crunch every time I took a step. Crunch, crunch, crunch, every step, all the way there…I was horrified once I reached the bathroom (which had lights). These bugs COATED the walls and floor (my parents have pictures, somewhere). Quite the traumatic experience for a 12-year-old who was not wearing shoes at the time. Nowadays, I almost never go outside barefoot.

    Reply
  • PHILLIP FALCONE
    April 8, 2014 8:14 am

    in around 1978-1982 approximately, in brooklyn, new york. i witnessed some flying insects with long stingers boring holes in a large (lightning damaged) tree in the front of my neighbors house, i was told that they were called mayflys. i was between the ages of 8-12 yrs old and didn’t do much more research regarding it assuming the information i received was correct. some years later i was in long island, new york climbing on the underside of some bleachers , beside a football field and i was stung by two of these same insects. upon closer inspection and extraction of the stinger, i noticed it had a three pronged stinger, one part was hard and sharp the other two parts were softer and intertwined with the main piercing stinger. i was telling someone about it and they said it couldn’t be a mayfly. so i went online to do more research, to find out if it was or wasn’t and what it could be. now i have read that mayflys don’t sting and it seems only male giant mayflys could fit the description of what stung me. i do not have images and in brooklyn there was no lake or pond for mayflys to have bred so close to the tree i witnessed them boring holes into. Which based on what i have read, could rule out most mayfly species, Also, I have not seen these insects again, in the last 25 years or more, i have no images but to my recollection they bore holes that were about 1/4 in diameter and at least deep enough that you couldn’t see how deep they were. the stingers were a minimum of 3 inches long, now i may be remembering a slightly more exaggerated stinger approaching 4-5 inches, but that can just be faulty memory or trauma induced memory. regardless, they were the same insects boring holes in the tree and made so many holes in fact the tree eventually collapsed and they most certainly stung me with little provocation. does anyone have any idea what these flying, boring , stinging insects were?

    Reply
    • Your entire description is a perfect fit to a Stump Stabber, a Giant Ichneumon in the genus Megarhyssa. The only thing that does not fit is your account of being stung. While we imagine that since the ovipositor can bore into wood, it is possible to be stung, it is our understanding that Stump Stabbers do not sting. According to Icheumon Wasps by Lloyd Eighme on Skagit.wsu: “It might frighten you, but if you could watch it long enough you would be amazed at what it does. It lands on the bark of a tree and crawls up and down, tapping with its long antennae, obviously searching for something. Eventually it finds the spot it is looking for and begins to drill into the bark with its long needle-like ovipositor. It has detected the larva of a horntail wasp chewing its tunnel in the wood an inch or more below the surface of the bark. The ovipositor is made up of three stiff threads, hardened by minerals, that fit together with a groove in the center. Vibrating those sharppointed threads forces them into the bark and sapwood of the tree to contact the horntail grub in its tunnel. An egg is forced down the ovipositor to parasitize the grub. If the ichneumon parasite larva killed its host, they would both die, trapped in the solid wood which the parasite is unable to chew. It only feeds on the nonvital organs like the fat body until its host has nearly completed its life cycle and has chewed its way out near the surface of the bark. Then it kills and consumes its host grub and completes its own life cycle to emerge as another giant ichneumon wasp in the genus Megarhyssa (mega=large; rhyssa=tail) to start over again. You can see both Megarhyssa and its horntail wasp host in the MG collection.
      People often ask if the ichneumon wasps will sting them with their needle-like ovipositors. The wasps are interested only in laying eggs in caterpillars or other insects, but if you handle a live one it may try to sting you in self-defense. Small ones could not likely penetrate your skin, but larger ones might be able to.”

      Reply
    • Your entire description is a perfect fit to a Stump Stabber, a Giant Ichneumon in the genus Megarhyssa. The only thing that does not fit is your account of being stung. While we imagine that since the ovipositor can bore into wood, it is possible to be stung, it is our understanding that Stump Stabbers do not sting. According to Icheumon Wasps by Lloyd Eighme on Skagit.wsu: “It might frighten you, but if you could watch it long enough you would be amazed at what it does. It lands on the bark of a tree and crawls up and down, tapping with its long antennae, obviously searching for something. Eventually it finds the spot it is looking for and begins to drill into the bark with its long needle-like ovipositor. It has detected the larva of a horntail wasp chewing its tunnel in the wood an inch or more below the surface of the bark. The ovipositor is made up of three stiff threads, hardened by minerals, that fit together with a groove in the center. Vibrating those sharppointed threads forces them into the bark and sapwood of the tree to contact the horntail grub in its tunnel. An egg is forced down the ovipositor to parasitize the grub. If the ichneumon parasite larva killed its host, they would both die, trapped in the solid wood which the parasite is unable to chew. It only feeds on the nonvital organs like the fat body until its host has nearly completed its life cycle and has chewed its way out near the surface of the bark. Then it kills and consumes its host grub and completes its own life cycle to emerge as another giant ichneumon wasp in the genus Megarhyssa (mega=large; rhyssa=tail) to start over again. You can see both Megarhyssa and its horntail wasp host in the MG collection.
      People often ask if the ichneumon wasps will sting them with their needle-like ovipositors. The wasps are interested only in laying eggs in caterpillars or other insects, but if you handle a live one it may try to sting you in self-defense. Small ones could not likely penetrate your skin, but larger ones might be able to.”

      Reply

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