…written by Buglife Cymru, NaB Scarce Yellow Sally Conservation Officer Sarah Hawkes.
Join Buglife Cymru’s, Nature am Byth Scarce Yellow Sally Conservation Officer, Sarah, as she recounts her journey of discovery during this years’ survey season for her project; she shares some of the highs, the lows and some fascinating new discoveries! (Part 2 of 2)
Wrexham’s rarest animal, Isogenus nubecula, the Scarce Yellow Sally, has emerged from the river waters for a brief 3-4 weeks as an adult stonefly. I’ve been tracking the emergence; counting exuvia (the cast skin left behind following an insect moult) on bridges & searching for sightings along the banks of the Welsh River Dee and keeping a brief record, join me as I continue my journey.
Saturday 3 May 2025: After two nights of sound recording with my little band of drummers, the Scarce Yellow Sallys have gone back to the river and their beats have gone off for analysis.
Whilst handing them over I was able to listen to another stonefly species rhythms – no louder, but much faster than the laconic Sally, and more buzzy. I am asking Tim to get onto it for his next insect featuring song.
Imogen and Katie from the “bug department” at Chester Zoo came out to the river on a couple of days and together we gathered lots of footage of the stoneflies mating, searching grasses, settling on trees and some images of the egg masses. I am hoping to get some better photos of the latter if we can get lucky with the weather and finding more animals later this week.
Alan, Mel and Kaitlyn also came over yesterday to help search the Ceiriog, but no luck so far and I have not been able to get to the bridge to see if there are any exuvia on the walls – the water is too deep even for waders!
We did find a lovely Violet Oil Beetle, and a pretty Snipe Fly at one of the Dee sites.
Tuesday 6 May 2025: After a frost early this morning, Imogen from Chester Zoo and I set off for an evening’s “Sally” hunt on the coldest day for ages. The forecast was OK, but not inspiring, so it was touch and go whether I could justify asking for volunteers to help, so I took Eira the dog as a companion in case there was nothing else to look at.
In fact we found 24 Scarce Yellow Sally in the trees, of which six were mating pairs!
It is so nice to be able to see and watch them. Knowing that almost nothing is known about their adult behaviour, we can ask ourselves the most naive questions and they are as valid as any other. That is really what this year’s survey season is for, to look and wonder why, ready to follow up with more targeted questions next year.
The “Sally” are in a few very localised places around Bangor on Dee up and down the River. It is good, I think, to encourage people to look out for this little animal and be proud of it and the River by their homes! If people send us photos of it, that helps us find out more, too!
Tuesday 13 May 2025: The endgame is upon the Scarce Yellow Sally. Most eggs are laid and there are fewer and fewer of them each time I visit. On Friday it was lovely to have Justin Williams, a local naturalist, along to see this rarest of Wrexham’s animals.
After searching for a while, we did manage to find some of the last few “Sallys” in the trees and the thistles.
Down by the River Dee it’s now the turn of the mayflies. Ephemera danica, Common Mayfly, are dancing vertically, up and down over the riverbank. Fragile Pale Watery Mayflies settle on the vegetation. Alderflies, click beetles and sawflies are all coming out to take their places as the season moves on.
It won’t be long now before you can spot the Yellow Mayfly (Potamanthus luteus) which has only recently moved North to the Dee, all the way from the Usk in the South, following the warming climate.
Friday 23 May 2025: One last visit, this time with the Natur am Byth central team who came over to experience the project for themselves and how I work when surveying along the river. It was another beautiful sunny day when I took them to see where we carry out the in-river surveys and the exuvia collections at Bangor. Then we moved to another site where we studied the adults. I had my fingers crossed behind my back, almost sure there wouldn’t be any “Sallys” still out on the river bank for them.
Gloriously, the Riverfly Gods smiled and Josie found a last male Sally under a branch.
Two days later I went back; there was no sign of any more.
Epilogue, of sorts…
Monday 2 June 2025: Today’s the day I had allocated for starting ‘engagement events’ in earnest, beginning with a day out for Wrexham University Fine Arts Students.
We walked along the riverbanks, looking at invertebrates and the river, discussing their ideas for art works (and wonderful first creations); interpreting their thoughts, following my earlier visits.
Heading up along the river as far as the Sand Martins’ nest site, before trying out kick sampling in the river when Debbie said ‘What’s this?’
I replied, ‘A Scarce Yellow Sally,’, then Tracy found one too and before we knew it there were four stoneflies (possibly five but one may have come round again for a second look!)
My confident prediction of the end of the season, back in May, was obviously way off: no surprise perhaps. How many times have I answered volunteer questions with ‘We just don’t know the answers yet but that is where you come in’?
So, here we are, into June and, whilst I ended the volunteering survey sessions on Tuesday 20 May, Scarce Yellow Sally has other ideas and in a moment of serendipity, the lovely art students stepped delightedly into the breach!
What a brilliant day for us all! And to ‘ice the cake’ – not that it needed it – we found large Potamanthus mayfly larvae in the kick samples (another target species for this project about to become a flying river fly!) ready to emerge as sub imagos at their next moult.
What can you do to help…?
If Sarah’s mini journal has piqued your interest and you want to get involved in our Scarce Yellow Sally project, please do get in touch. We are particularly interested in help between April and June, when we are asking the public to help us locate, photograph and report any sightings of stoneflies along rivers in Wales. But it is likely that sightings outside of these times are of interest too particularly given Sarah’s experience with the Wrexham University students this year.
If you live outside of the project area but think you may have found a Scarce Yellow Sally, please record your sighting via our Search for the Scarce Yellow Sally web form too.
Main Image Credit: Scarce Yellow Sally (Isogenus nubecula) © Sarah Hawkes