Mayfly Facts

Shadflies, also known as Mayflies, belong to the order Ephemeroptera. There are 3,000 species of mayflies in the world. 

Among the earliest insects to appear on planet Earth, the mayflies date back more than 350 million years. You can find them in the rivers, streams, ponds, and lakes under rocks, decaying plants, and sediments. 

Environmental changes and habitat loss are the major threats to mayfly survival in the wild. Some species of mayflies are considered endangered or threatened.

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Mayfly Facts for Kids

  • Mayflies are an aquatic insect
  • They can grow to a length of 0.5 to 1 inch.
  • Green is the predominant color of most species of mayflies.
  • They supply food for fish, frogs, newts, and birds.
  • Mayflies hatch from spring to autumn.
  • The lifespan of mayflies is incredibly short (Few minutes to a few days).
  • It is estimated that there are over 2,500 mayfly species of mayflies in existence.

Life cycle

It has four life stages: the egg, the nymph, the subimago, and the imago. Let have a quick look at each stage below

The Egg Stage

Females lay eggs in the water at mating. The eggs fall to the bottom where they stay on small rocks, plants, and sometimes streambeds. 

Their size varies based on the type of Mayfly. The eggs take one to three months to develop, depending on temperature. This is the stage in which the mouth, legs, tail, and other organs develop.

The Larva Stage (nymph)

Mayflies have aquatic larvae (called mayfly nymph or mayfly naiad) that survive for a few months to a year in freshwater. A naiad molts upward of 20 times during its lifetime as it develops.

The Adult Mayfly Stage (subimago)

Mayflies are a little unique because they normally make one more molt just after acquiring operational wings. This is called the alate stage. Usually very short, this stage is generally only around 30 minutes to a day-long, all depending on the species. 

Imagos in the adult form reproduce and disperse; they don’t eat. The stage is perfect for numerous fish, and many ‘fishing flies’ are modeled on them.

The Hatch Stage(imago)

It is very common that the whole mayfly population comes to maturity at once. This is referred to as the Hatch.

During the Spring or Autumn, you’ll see mayflies everywhere. They dance around and rest and relax on all the available surfaces. 

Mating is usually carried out in mid-air. Nevertheless, the mayflies have achieved a great deal of success. 

A news event for several years, the Hatch in La Crosse, Wisconsin, is so big that it is visible on radars. As the mayflies emerge, they land everywhere and cover some parts of the area like snow.

What’s in a name

The Mayfly has several names. 

They are commonly referred to as Canadian Soldiers in the United States. It is known by the names fishfly and shadfly in Michigan and Canada. The British call them Up-Winged flies. 

Also known as salmon flies and June bugs.


Carnivorous invertebrates and fish prey on mayfly nymphs. A number of predators, including hornets, dragonflies, and robber flies, consume them easily during the wingless stages. 

The mayfly, when resting, is preyed on by spiders, beetles, birds, and certain mammals, including flying squirrels in North America. 

Mayflies are particularly vulnerable to predation from fishes during their transformation into adults and during oviposition by females.

What else do we know about the Mayfly

Mayflies have existed for about 350 million years. They existed before the dinosaurs did, then they survived the Extinction.

Mayflies have large compound eyes, two long tails, flexible antennae, narrow bodies, and membranous transparent wings. Wings are kept upright when they are not in use, with the first pair being much larger than the second pair.

Females and males have two sets of genitalia. The male has two penis-like organs, while the female has two openings. Additionally, males have larger eyes than females, helping them detect mates during the breeding mating season.

In the larval stage, mayflies consume algae. The funny thing is adults do not have fully functional mouths and do not actually eat. Frogs, newts, trout, bass, and catfish find the mayflies as an important source of food.

The female lays thousands of eggs slightly underwater. Usually, they sink to the bottom of the water and mayfly hatch about 6 weeks later.

The most important times for the emergence of adult mayflies are spring and autumn. Only a few species hatch in May. The mayfly’s subimago stage is a unique developmental transitional stage. Mayflies in the subimago phase are molting for one last time before becoming sexually mature.

Mayflies have a short lifespan. Adults live anywhere between a few minutes and several days. Reproduction is their only purpose, and once done, they die.

There are only a few species that emerge in May, thus the name “Mayflies.” In fact, many other species emerge in the summer months, so the term does not seem to apply to them.

The Ephemeroptera family (class and scientific name) are known collectively as Mayflies. The Greek word Ephemeroptera means “lasting for a day.” Because of this, they are also called one-day insects or one-day flies.

In order to survive, mayflies require clean water environments. Pollution makes them unable to survive. A greater abundance of Mayfly larvae in a particular body of water can indicate the quality of that body of water.