Before this section begins to groan under the weight of Large Dark Olives through winter here's what's probably an Small Dark Olive - although I'm not sure, any opinion on the ID gratefully received..








The specimen a small fly with a body length of about 5.5mm - this one's a female imago or spinner which makes it hard to identify - small differences in male genitalia are generally the distinguishing feature in this group of flies.

For size reference the hook alongside the fly is a barbless size 18 Kamasan B981



Olives belong to the family Ephemeroptera which is classified as being close to the dragonflies and share their characteristic of having two pairs of wings. Earliest fossil remains from Permian shales in Kansas show the Ephemeroptera originally had fore wings and hind wings of similar sizes
but as time passed the size of the hind wings gradually became reduced. Some Baetidae have very small hind wings and the specimen belongs to this group - the photo below shows the right hind wing of the specimen shaded in blue.



Hind wings are one of the features studied in the process of determining the identity of a specimen, this specimen has a small projection on it's hind wing known as a costal node or costal process.



Here's a diagram showing a fore wing and hind wing of a member of the Baetidae family - note the costal process



......and here's an image edited to display the hind wing rather than the fly -



The small oval hind wing and its costal node is a distinction which belonging to one of five species of Baetidae known collectively as the genus Baetis - Baetis buceratus, B. fuscatus, B. rhodani, B. scambus or B.vernus.

The only species I feel confident in discounting is the LDO, the remaining female spinners are so similar that I'm taking a wild guess that the specimen is Small Dark Olive due to the fact that it has nearly black eyes.
Any ideas?

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NOT A CLUE!

But this is going to be a brilliant thread, will certainly help us numb nuts to identify some of the fly life on our waters.

Thanks Col,

Mostyn

Thanks Mostyn. Makes you realise how the size 20s down are the only way to make a decent imitation of the smaller upwings.

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Nice images diawl bach.


A shade darker around the thorax and I would almost have thought "Iron Blue", as her rear wing shape seems correct.






I've a diagram on the subject of what was then the costal projection from 'An Angler's Entomology' 1952 J.R.Harris.

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Save the softmouth trout

Nice pictures. clarity would certainly help me. We also have small spur wings and they are so similar in colour and size at the dun stage. Ans they are so small it is really hard to identify down at the water.
We had many of these hatching mid morn-mid afternoon last week.

Here are two pictures i took this year which i believe is the male and female duns.


male dun SDO


female dun SDO
By the way as a matter of scale the silver reel band on my rod is 5mm. that fly is tiny.


Someone like old bull will have to complete the set with the male spinner

I've attached a couple of images of the male Small Dark Olive Dun taken back in May; the hindwing is a crop so has lost some of it's sharpness but still shows plenty of the detail.

The problem with identifying the Small Dark Olive female spinners is that they are almost anatomically identical to those of the Pale Watery and both are on wing during the period May - October. So if there were orange-red eyed males about then I'd go with Small Dark Olive.

I’ve removed this image because of unauthorised use after it had been downloaded from the forum – all my images bear a copy-right signature so they clearly should not be used without having first obtained permission. I’m disappointed to have to do this but feel I don’t have much option.

When these insects are photographed using a macro facility, it amazes me how different they are, yet when on the wing, it's so easy to misinterpreted the species viewed at the time! With aging eyesight I continually mistake one species or type of fly for another - LDO covers a multitude of flies on the water, : Small Olives, LDO's, Olive Uprights, Light Olives, BWO's, and we're just skimming the surface of up-winged flies. Love this thread; could turn out to be fascinating! Hopefully.

keep the photos coming.

Thanks for taking the time to post your observations and pictures - no conclusions so far though and by the look of it it will remain one of the unknowns.
As Ray says an association with some males would help but none came to the net that day.

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