“Mayflies are unique among insects in having a penultimate ‘subimago’ stage, which like the adult has wings, but unlike the adult has no genitals.”
Arthropod Quarterly Digest
All throughout each teenage year,
I spend my evenings by the brook –
In Spring I love to dawdle here
To watch the ducks or read a book.
I sometimes bring some fishing gear,
Though rarely bother with a hook.
My friends pair-off in woods or laybys,
I, though, spend my time with mayflies.
We are a lot alike, Ephemeroptera.
We spent our childhoods trapped within backwater gloom,
Just waiting for that feeling that it’s time to bloom –
But when we shed our skins and gain our wings,
What did we find, Ephemeroptera ?
Our flight is drunken and unsteady,
Bodies new are strange and heady,
Maybe we are not so ready yet,
To put away our childhood things.
But on it comes: from nymph to fly –
To moult, to mate, to lay our eggs, and die.
We’re subimago adolescents,
Buzzing with a shared frustration,
Trapped within the boring present
Waiting for our next gestation –
Damn, the urge is so incessant,
Yet we cannot reach elation !
Metamorphosis, you cheat,
We’re naiads still and incomplete !
I know a lot about Ephemeroptera,
These One-Day Wings that flit and dart about the creek.
I spend my teenage evenings watching, week by week,
While all the while, my classmates grow up too.
I ought to leave, Ephemeroptera,
I ought to leave, but I’m afraid –
I still do not feel fully made.
And so I watch you rise and fade,
And wonder when my final moult is due.
Will I change soon, oh Flies of May ?,
To start the years that form my final day.
To expand on the quotation in the epigraph, mayflies are primitive insects that have changed far less than those restless ants and beetles. They show little difference between nymph and adult (well, except that the former lives in water and has no wings), and most bizarrely they have two consecutive flying stages. If you see any other insect with wings, then it is an adult and will never shed it’s exoskeleton or pupate again. Perhaps those giant early griffinflies of the Permian also had two (or more) instars on the wing – they were after all comtemporaries of the first mayflies. Or perhaps it’s a later mutation that avoids having to build both wings and genitls in one hit without the benefit of a lengthy pupation.
Anyway, when it is time, the nymph pulls itself out of the water either onto the water tension of the surface, or up some vegetation stalks. There it rests, moults, and dries its cloudy new wings – these already contain the adult wings within them which are revealed when that cloudy layer is shed. In a few species, the females stop here and never make the final moult, while in others the females can survive for a couple of weeks – long enough for their already-getated eggs to hatch the moment she lays them on the water surface, so in terms of the poem calling them ‘one-day wings’ might be a little disengenuous, but hell, it’s too good a line to drop. A friend also suggested that I had my metaphor the wrong waya bout – teenagers aren’t subimagos because they do have the hormones, they just don’t have the transport.