Are Fish Flies and Mayflies the Same Thing?

September 17, 2020

Are Fish Flies and Mayflies the Same Thing?

A lot of people often mistake a fish fly for a mayfly. In all honesty, we were not sure if there were any differences between them until recently!

Are fish flies and mayflies the same thing?

The short answer is no. After some research, we found out that a mayfly is the correct term to describe the millions of Ephemeroptera that emerge from Lake Erie and other nearby lakes.

On the other hand, a fish fly is an entirely different group of insects, scientifically known as Corydalidae. Although they may look similar, they are indeed not the same type of insect.

But what’s the reason behind this confusion? Let’s find out.

Why People Think Fish Flies and Mayflies are the Same

As you know, people from different regions or countries can sometimes have different names for the same thing.  A famous example is the English ‘biscuit’ and the American ‘cookie.’

The thing is that, in Canada, people used the term ‘fish fly’ to describe the insect group of Ephemeroptera. Even though this word is widely known in Canada, scientists emphasize that it should be used with another insect group. This group is the Corydalidae.

As a result, you can only expect some confusion. Because people heard Canadians refer to mayflies as fish flies, they assumed they were the same thing. Let’s now talk about how fish flies and mayflies are actually fairly similar.

How Fish Flies and Mayflies Are Similar

Palingenia Longicauda

It is not the difference in terminology that may have caused this incorrect assumption about these two insect groups. If you learn more about their characteristics, you’ll notice that they have a few things in common.

For instance, they are both aquatic insects. This means that they thrive and hatch their eggs around water bodies, especially rivers, streams, and lakes. They are found around fresh, clean water, where they can feed on smaller aquatic insects.

Fish flies and mayflies both begin their lives in these aquatic forms. They emerge from their eggs in around unpolluted water environments and crawl into the water when they are a bit older.

However, this is the furthest that their similarities would go. Quite frankly, it’s strange how some people still believe they’re the same thing because their differences are many.

How Fish Flies and Mayflies Are Different

Now that we got that out of the way, let’s talk about their differences. You will notice that there are a lot of differences between these two insects. Let’s discuss them more in-depth.


The first thing that tells both types of insects apart is their appearance. If you take a glance at both, you will quickly understand what we’re talking about.

An adult fish fly is larger than a mayfly of the same age. Not just that, the shape of a fish fly’s body is entirely different since it’s a bit closer to the shape of a common fruit fly or moth.

The males have feathery antennae that are quite similar to large moths. Also, they have eyes and jaws that are not noticeable to the naked eye.

On the other hand, a mayfly looks a lot like a dragonfly. It has a long, thin tail and large wings that do not fold over its abdomen. Plus, you will notice that it has a longer body than a fish fly.

Immature Stages

As we previously pointed out, both types of insects begin their lives around freshwater bodies in aquatic forms. Still, their immature stages aren’t identical. This is one of the main ways you can tell the difference and determine which species lives in your region.

Fish flies lay their eggs on vegetation that surround streams. After that, the eggs hatch, and the larvae crawl out and into the water. Then, they prey on other smaller aquatic animals or even plants.

Most commonly, fish flies will feed on vertebrates such as minnows and tadpoles.

Once they’re large enough to transform into pupae, they get out of the water to the bank. In this stage, you’ll be more likely to find them in cavities under stones or under barks of trees.

When it comes to mayflies, you’ll notice that their behavior in the early stages of their lives is another story. They start their lives as naiads or nymphs, present in clean, fresh water to prey on other aquatic animals.

Then, they emerge from the water as adults with full wings and large bodies. In a unique display that attracts many tourists, fully-grown mayflies come out of the water in significant numbers from spring to autumn.

Even though they are called mayflies, they don’t come out in May exclusively. But this is often when they hatch in large numbers.


Mayfly and ripple on still water

Fish flies and mayflies have different lifespans as well.

Fish flies can live up to several years. Yet, the most noteworthy thing about their lives is that they spend only about seven days as adults. Therefore, fish flies spend most of their lives in larvae form.

The lifespan of mayflies is one year; most of it spent in the water as nymphs. Surprisingly, adults get to live for a day or two once they are out of the water.

Effects on Humans

Mayflies have had a considerable impact on humans for years, while the same can’t be said about fish flies. However, it’s fair to say that the existence of fish flies around water bodies has been seen as an indication of the quality of the water.

Also, since fish flies only live for a few days, there isn’t much interaction with humans, even when they swarm an entire area. Most people will just ignore them since they won’t last for long.

On the other hand, mayflies have twisted their way into our lives in unusual ways. Yes, their lifespans can be much shorter than fish flies, but it seems like they have left an impression on us.

Fly Fishing

The most common practice that links mayflies to humans is fishing. Wondering how this is possible? We’d be glad to explain.

The first thing you should know is that mayflies are prey to fish in all their different life stages. Most importantly, they’re the main ingredient in the diet of trout.

Fishermen noticed this and began to model artificial mayflies to attach to their hooks. Also, they made different versions of their baits to resemble the various life-cycle stages of mayflies.

Of course, this way, they’ll be able to catch all shapes and sizes of fish by mimicking the type of food they’re attracted to.

Over the years, these artificial versions of mayflies became more advanced to resemble the original insects better. The way that these manufactured copies moved and looked were identical to the real thing to lure freshwater trout.

In-depth studies and research on the habitat, morphology, and behavior of mayflies had to be made to create these artificial versions. Therefore, you can quickly see how these little insects revolutionized fishing, creating the term ‘fly fishing.’

If you want to learn more about fly fishing, check out our articles on fly fishing for steelhead and our article on fly fishing for tarpon.

Tourist Attraction


Mayflies emerge out of the water in huge numbers, which might be annoying to locals. Yet, this spectacle might be a favorite of tourists who don’t usually see swarms of mayflies in their hometown.


In some cultures, especially Asian countries, mayflies are consumed as much as a type of meat. According to studies, mayflies contain a large amount of raw protein, probably more than any other insect.

Therefore, people in these regions collect mayflies, particularly in adult form, to cook or eat raw. Also, they can be dried and preserved to be used with other types of food.

Other Human Uses

There are other ways that mayflies have had a lasting impact on humans.

For instance, they’ve been used as bioindicators to test the quality of water in ecological assessments. As we mentioned earlier, the reason behind this is that mayfly larvae don’t survive in polluted aquatic environments. Therefore, they have become important for studies and research over the years.

Also, many scholars have studied the shape of a mayfly’s body and the mechanism of its wings. These scientists claimed that, by doing so, they could get a better glimpse into the evolution of insect wings and its relation to the gill theory.

If you’re looking for another evidence of how mayflies were ingrained in human culture, you may want to take a look at one of Nike’s creations in 2003. The famous brand released a line of running shoes under the name ‘Mayfly.’

Their design included a pattern that paid homage to a mayfly’s wing, elegant, sleek, and durable. Humans have been taking inspiration from how animals have evolved for their design for hundreds of years. Therefore, you can see that, unlike fish flies, people are quite familiar with mayflies.

Wrapping Up

Due to a lost-in-translation mistake, people have been mixing between two groups of insects for years. As a result, this begs for an important question. Are fish flies and mayflies the same thing?

After skimming this article, you now understand that fish flies and mayflies are entirely different. They have unrelated traits when it comes to appearance, immature form, and even lifespan.

The most noteworthy difference, though, is their interaction with humans. While fish flies are known to some people, mayflies are more popular, especially because of their association with fishing.

Now, the next time someone can’t tell the difference between a fish fly and a mayfly, you’ll know precisely how to direct them on the right path!

Happy Hunting!

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