#42 Double Kidney by Charles Fletcher
Meet Charles Fletcher, Yorkshire County Moth Recorder!
Charles spent 33 years on the front line as a general practitioner in Ripon. Having retired in 2015, he had imagined there would be more spare time to indulge in his interest of moth recording, but family and other interests somehow keep getting in the way. Interested in natural history as a child, mostly birds and butterflies, he thought moths were far too difficult to record, until a friend put a moth trap in his garden one night. The following morning, he was amazed to find it full of huge variety of moths. After a couple more sessions, he was surprised to find that he could identify quite a few of them. He attended meetings of like-minded people, and due to an annoying habit of putting his hand up and volunteering, found himself installed as county macro recorder a few years later, a role he has held for the last 15 years. Moth recording has become increasingly popular since then, and he is currently dealing with almost a quarter of a million records per year. Charles can be contacted on chfletcher@btinternet.com and you can follow him on Twitter at @DoubleKidney – a clue about his chosen species.
Charles has chosen the moth Double Kidney Ipimorpha retusa. He comments “Wherever you live in our wonderful and diverse county, there is usually an animal or plant that is “special” to your area and tends not to occur elsewhere. In my case, living near Ripon, there are many contenders, but my favourite is the moth Double Kidney. Not the most brightly-coloured or showy species perhaps, but it always gives me a thrill when I catch it, as few moth trappers in the north of England have ever seen one. It is a moth shrouded in mystery. Why is its home in a small area of damp woodland north of Ripon the only place it occurs within 150 miles? Is it hiding undetected in other locations? So special is this moth, that it is my Twitter “handle.” Yes, I am Double Kidney.” You can find out more about this species on the Yorkshire Moths website at https://yorkshiremoths.co.uk/.
Double Kidney is a moth of damp woodland, the bulk of the population being in south and south-east England, and south and west Wales. Even there it is never particularly common and only recorded in small numbers. Many years ago it must have been more widespread, though it appears to have been always very local in the north of England, and central Yorkshire was its northern outpost. William Porritt wrote in 1883 “We only have one locality for this local species. Askham Bog.” - this record was credited to William Prest who collected widely at the Bog. We have another old record from 1886 at Birstwith, attributed to F.T. Walker. It was evidently still present at Askham Bog some years later as Rutherford stated that it was present “early in the century but none since” and he also noted larvae on willow at Riccall in 1940. He included it in his 1971 list of species thought to be extinct in the county but marked it “overlooked?” and commented “may have receded southwards.”
Double Kidney HC 1707/21
In 1983, regular moth trapping began to take place at High Batts Nature Reserve, 32 acres of wet woodland, close to the river Ure just north of Ripon. Almost immediately Double Kidney was found to be resident, further north than it had ever been found in the country. Since 2007, the moth has been also noted regularly, often in good numbers, at Bellflask Fisheries, close to High Batts on the other side of the river. Before the 1980s, these sites had been ignored by lepidopterists, so it is highly likely the moth has always been resident there.
A recent increase in moth trapping at both these sites has shown that Double Kidney is thriving, particularly at Jetty Wood, part of the Bellflask area. An incredible 61 in a single trap on 23/7/2021 gives an idea of the size of the population. Single wandering moths occasionally turn up at Hutton Conyers and Sharow, three and four miles respectively to the south-east, suggesting that there might be some breeding a mile or two further downstream. Moths have never been recorded further north.
So, the current situation is that we appear to have a small but thriving relict population. This is the only one in the north of England, as moths from the old Cheshire population have not been seen since 1996. The nearest current sites where it occurs, in Shropshire and Herefordshire, and on the Norfolk Broads (particularly the Yare Valley), are about 150 miles away. This raises several questions: what makes this small patch of woodland so special for this species? Which species of willow does it prefer? Larvae have been found at Bellflask on Purple Willow Salix purpurea, but is this the only food plant? European literature suggests Grey Willow Salix cinerea is its favourite food plant, and some authors suggest other willow species plus Black Poplar Populus nigra. Are there other undiscovered populations? If it can hide for many years at its current site, is it hiding elsewhere? There are still many areas in the county which have never seen a moth trap, and unexplored wet woodland further down the Ure or even along the Swale could well harbour populations of this species. We just need to go out and look for it. As with other blogs in the series, this again highlights just how much is out there to be discovered, even in taxa with a rich recording history and dedicated community of current recorders.
Recording and monitoring
Double Kidney and The Olive 08/08/03
The main population is being monitored closely at Bellflask, where a mercury vapour trap is operated most nights. Regular moth trapping also takes place at High Batts NR. It is difficult to accept that the only moths in the north of England occur in such a small area and it may well occur elsewhere. Damp woodland with plenty of willows should be targeted further downstream. The lower Ure, lower Swale, and the Ouse both above and below York could spring surprises. The old 1940 record at Riccall, close to the Ouse, is interesting, and areas nearby could be worth targeting. There is also an unconfirmed record from Strensall Common in 1991 on the YWT database and the NBN Atlas, though this is less likely as there has been a considerable amount of trapping on the common in recent years. Care should be taken not to confuse it with the rather similar Olive Ipimorpha subtusa which has a less “hooked” forewing and cross lines which converge towards the trailing edge of the wing. These lines are more parallel in Double Kidney, which is also browner and less olive-coloured.
Further information and acknowledgements
NEYEDC would like to thank Charles for his time and expertise in helping to create this blog.