Rhithrogena picteti (Mayfly)

Images of undisturbed subjects in their natural environment. All subject types.

Moderators: rjlittlefield, ChrisR, Chris S., Pau

Peter Maihoefer
Posts: 52
Joined: Thu May 20, 2021 5:35 am
Location: Southern part of Germany

Rhithrogena picteti (Mayfly)

Post by Peter Maihoefer »

Rhithrogena is a genus of flatheaded mayflies in the family Heptageniidae.
Found the larvae in a small clear creek. During my fotosession the subimago start the skinning. Only Mayflies have a Stadium called "Subimago".
Attachments
Imago with exuvie
Imago with exuvie
Transformation: Subimago to Imago
Transformation: Subimago to Imago

Pau
Site Admin
Posts: 6051
Joined: Wed Jan 20, 2010 8:57 am
Location: Valencia, Spain

Re: Rhithrogena picteti (Mayfly)

Post by Pau »

Excellent pictures and sequence!

Welcome to the forum, Peter
Pau

Peter Maihoefer
Posts: 52
Joined: Thu May 20, 2021 5:35 am
Location: Southern part of Germany

Re: Rhithrogena picteti (Mayfly)

Post by Peter Maihoefer »

Thanks Pau, for the first and nice comment.

Peter

MarkSturtevant
Posts: 1946
Joined: Sat Nov 21, 2015 6:52 pm
Location: Michigan, U.S.A.
Contact:

Re: Rhithrogena picteti (Mayfly)

Post by MarkSturtevant »

Very interesting. I've seen that stage, but not often as they don't last very long.
Mark Sturtevant
Dept. of Still Waters

Peter Maihoefer
Posts: 52
Joined: Thu May 20, 2021 5:35 am
Location: Southern part of Germany

Re: Rhithrogena picteti (Mayfly)

Post by Peter Maihoefer »

Thanks for viewing and comment.

I put the pictures togehter. Every part of the summary ist one picture. This is better for an overlook. The best view is to cross-fade the seperat pictures in a presentation.

It was very difficult, because I didn´t expect the transformation. At first was a 63er luminar on a bellows, but with ongoing of the transformation the Insect with the exuvie grow and it was not possible to catch both with the luminar. So, camera away from the bellows, 100 mm Makro on the cam, bellows down from the tripod, cam on the tripod, next pictures..........

rjlittlefield
Site Admin
Posts: 23561
Joined: Tue Aug 01, 2006 8:34 am
Location: Richland, Washington State, USA
Contact:

Re: Rhithrogena picteti (Mayfly)

Post by rjlittlefield »

I'm a little late to the party, but I'd just like to add that I think this thread and your other one HERE are both beautiful and fascinating. Very nicely done!

For years I have wondered how mayflies manage to cleanly extract a set of functioning wings from between the layers of a slightly thicker set of functioning wings, neatly leaving behind the old outer membranes as if they were just a collapsed balloon.

Does anybody know a detailed explanation for how that magic is accomplished?

--Rik

Peter Maihoefer
Posts: 52
Joined: Thu May 20, 2021 5:35 am
Location: Southern part of Germany

Re: Rhithrogena picteti (Mayfly)

Post by Peter Maihoefer »

I am just a private mayfly worker and a flyfisher, but not a professional entomologist.

The first thing is, that we do not know why mayflies have a subimago stadium. No other flying insect have a subimago stadium. Why doesn´t loose the mayflies this stadium in the evolution like the other insects?

The transformation is risky. Several mayflies cant´t finish this act. During the transformation they are an easy prey for predators.

One reason could be, that the wings of the subimago have hairs which hold the water away. Have a look to my added picture of Habroleptoides confusa.

If you compare the subimago and the imago, the tails (cerci) and the first leg pair of the imago ist extended. The direct hatch form the larva to a flying insect allows not this process. This could be the second reason. The male mayflies need the long tails and the long first legs for the pairing dance. Without that extension no copulation in the flight is possible.

I guess that the wings of the subimago have two layers. Outside the Subimago layer, inside the imago layer. The outside layer ist very thin. Inside is the real strong wing. During the transformation the mayfly loose only the very thin skin.

If someone know it better - please share your knowledge.

I hope my english (and the helps of the translator) is good enough to understand that I would like to say.

Peter
Attachments
Habroleptoides confusa.jpg

zook
Posts: 118
Joined: Wed Feb 28, 2018 3:08 pm
Location: zemun/serbia/milky way

Re: Rhithrogena picteti (Mayfly)

Post by zook »

Great shots, especially the first and stage change sequences!

SvenOstermann
Posts: 5
Joined: Thu May 22, 2014 2:49 am
Location: Germany, NRW

Re: Rhithrogena picteti (Mayfly)

Post by SvenOstermann »

Hello all,

Mayflies are the only insects that completely moult again in the adult stage. The nymph first hatches into a flying insect with milky cloudy wings, in this stage we speak of a subimago. Depending on the species, a second molt occurs a few seconds, but also hours or days later to the so-called imago stage. This can be recognized by the fact that the wings are now crystal clear.

Hope this helps.

Many greetings
Sven

MarkSturtevant
Posts: 1946
Joined: Sat Nov 21, 2015 6:52 pm
Location: Michigan, U.S.A.
Contact:

Re: Rhithrogena picteti (Mayfly)

Post by MarkSturtevant »

VERY late to the party. I can only add some small details to the questions of 'how' and 'why' they have a subimago stage
For how, it will be because the subimago is not entirely different from an insect nymph. They have full sized wings and can fly, of course, but other than that it will be similar in that to molt, insect wings will have epithelial cells in the wing membrane areas. This is necessary bc the cells are what lay down the cuticle for the later stage. After the epithelia lays down a new wing membrane cuticle, the cells then die, leaving behind the cuticle and a much lighter wing. What the exact schedule of this is for the mayfly subimago, I do not know. But the cells must have died before the insect molts to the imago, of course.
In order to molt, an insect inflates itself with both fluid and air, and this helps force a clean separation between the to-be-discarded cuticle and the new cuticle. There is also a fluid (a lubricant?) injected between the cuticle layers. Molting is done by rapid peristalsis-like contractions, and it does not always work. Many will get stuck in their old cuticle. This is a general risk of molting. But if one watches an insect molt very closely, you can see the muscular contractions moving along. From a distance it looks like they just slowly slide out. But in truth its a lot of frantic work.
As for why ... well there are to me different kinds of why's and they are all speculations. Some of these are ideas that there is some sort of evolutionary adaptation involved. There is experimental evidence that the subimago stage is to buy time to add on the features of the adult like the extra long front legs and long cerci. Although in truth, many insect nymphs manage to add on some pretty drastic changes before they molt to the adult form. My own hypothesis, which is mine, is that the subimago could be an adaptation to help synchronize their transformation to sexually mature adults, resulting in their being able to perform their brief nuptial flight along with 1000s of other mayflies. This improves the chances of mating while also overwhelming predators by their sheer numbers.
Yet another why is that it could be for no real adaptive reason at all. It could instead be an evolutionary hold-over from earlier times when insects molted all of their lives. Even as adults. Incredibly, insects are now understood to have evolved from within the Crustacea (so are technically Crustaceans!), and those arthropods typically don't stop molting.
Mark Sturtevant
Dept. of Still Waters

Peter Maihoefer
Posts: 52
Joined: Thu May 20, 2021 5:35 am
Location: Southern part of Germany

Re: Rhithrogena picteti (Mayfly)

Post by Peter Maihoefer »

Thank you Mark for the explanation.

Post Reply Previous topicNext topic