Here is a simple diagram and explanation of a mayfly lifecycle.  A mayfly is an aquatic insect that lives in clean, pure rivers and lakes throughout the Rocky Mountains and world.

The other day I talked a little bit about how unique mayflies are because they have such a short adult lifespan.  Now I wanted to give you a better understanding of how the entire mayfly lifecycle works because it is pretty neat.  I mean, how many animals do you know that live almost their entire life underwater and then come above water to live for a very short time just to reproduce before dying?  I can’t think of very many.

Mayfly Lifecycle Diagram

Here is a simplified diagram that shows the life of a mayfly.

Stages Of The Mayfly Lifecycle

As with all insects, a mayfly undergoes metamorphosis during its life.  This means that it changes its form from when it is first born until it is an adult capable of reproducing and having babies.

Nymph – This is the larval stage of a mayfly.  When a new mayfly hatches from an egg it is as a nymph.  A nymph lives underwater and has gills, like a fish, to breathe.  The nymphs tend to live on the bottom of streams or lakes under rocks where they eat algae.

Surprisingly (to me at least when I first learned this) a mayfly spends most of its life living as a nymph under water.  They will be a nymph for up to 2-3 years.

Emerger – Once the nymph is ready to move on to the next stage in its life it needs to undergo a metamorphosis to a winged insect.  As it undergoes this change it will rise to the surface of the water, come out of its skin, dry its wings and fly off.

Dun Or Subimago – A mayfly is the only aquatic insect that has two adult phases in its lifecycle.  When it first emerges from the water it is a dull colored dun or subimago, incapable of reproducing.  This is a very short phase, lasting from a few minutes up to a day.

Spinner – This is what makes the mayfly lifecycle so cool and unique.  Somehow, the mayfly undergoes one more change as a winged insect from the dun to a full grown adult, called a spinner.  The spinner is more colorful and its only goal in life is to reproduce.  In fact, this full grown adult can’t even eat food since it has no mouth part!

What a crazy strategy!  This aquatic insect decided that rather than have a mouth it will just focus completely and totally on reproduction.  Once it reproduces, the female returns to the water where she lays her eggs.  The eggs sink down to the bottom of the water, where they wait to hatch.

Once the adults have reproduced or laid eggs their life ends.  The female simply falls on the water, spent, exhausted and lies with her wings open on the water.  Fish swim along and slurp up the nice meal.  On the other hand, the males usually fly off into the weeds or plants on the side of the river to die.