Nemoura dubitans

The first few below were identified using the old RES key. Further down, the 2023 specimens were identified using the new FBA guide and the process seemed to be muuch more straightforward. Note that the FBA guide refers to the "pre-genital plate" whereas the old RES key calls this sternite 7. The shape of sternite 9 isn't described in the FBA guide.

By the time I examined these sepcimens they were a little too dried and shrivelled to be able to see the detail of the abdomen tips so I soaked them in potassium hydroxide solution to enable this. In hindsight I wish I'd not left them in for long, as it made it harder to see the unsclerotised edge of sternite 7. To make matters worse, for the first two I detached the end of the abdomen after sternite 7, which made it harder than necessary to view this (fortunately I did at least retain all of it). Looking at photos of fresh specimens the necessary details should have been easy enough to see without clearing at all if only I'd looked at them before they'd started shrivelling up.

female Nemoura dubitans showing abdomen tip (including close-up of one side) and sternite 7, Wendling Beck Environment Project (Norfolk, UK), 11th April 2022

different female Nemoura dubitans showing abdomen tip and sternite 7, Wendling Beck Environment Project (Norfolk, UK), 11th April 2022

On this one I did take a picture of the underside of its abdomen while it was still alive but it wasn't clear enough to see all the necessary details.

female Nemoura dubitans showing abdomen tip including sternite 7, North Elmham railway (Norfolk, UK), 9th April 2022

I haven't mastered how best to prepare these yet! Here I couldn't see the relevant details clearly enough without macerating the abdomen, but time I removed it from the potassium hydroxide before it was over-cleared. All the relevant features were clearly visible, but the dark shapes against a dark background didn't photograph well. So I then attempted to remove the gunk from inside the abdomen, but I again lost the definition of the edge of sternite 7 and the projection on sternite 9. This individual came to light (LEDs) - I think the first time I've had a stonefly attracted to light.

female Nemoura dubitans showing abdomen tip including sternite 7 (dry and cleared), Wendling Beck Environment Project (Norfolk, UK), 1st May 2022

The following were identified using the FBA guide. Note that for the female I couldn't make out the details without first clearing the abdomen even though the specimen was freshly dead. I could just make out the epiproct prior to clearing but it was a great deal easier to see after clearing. The first male and the female were swept together from a piece of grass where I had seen one land.

female Nemoura dubitans showing pre-genital plate, Wendling Beck Environment Project (Norfolk, UK), 29th April 2023

male Nemoura dubitans showing epiproct (in situ and detached for clarity), Wendling Beck Environment Project (Norfolk, UK), 29th April 2023

These two weren't coupled when I caught them but soon made the most of each others' company in the pot.

same male and female Nemoura dubitans, Wendling Beck Environment Project (Norfolk, UK), 29th April 2023

This male was netted in the same area as the last pair.

different male Nemoura dubitans showing forewing and epiproct (before and after clearing), Wendling Beck Environment Project (Norfolk, UK), 29th April 2023