On the 19th of September 2022, I made a last second change of mind to head for the coast instead of inland to do a short session. The destination was below Arklow Rock in south east Co. Wicklow on the beach below a cliff at grid reference T252706. It requires a 1.2km hike along the edge of a huge quarry and down 3/4 of the said beach! Not exactly an easy location to cart a trap or two as well!
This site was worth the effort as it was proving rather special for invertebrates with a large colony of Dark Bush Cricket Pholidoptera griseoaptera, Broom-tip Chesias rufata, L-album Wainscot Mythimna l-album, Sharp-angled Peacock Macaria alternata among many other good species. I had only been trapping this location and nearby spots around the quarry grounds for a year. The habitat is particularly rare with not only a beach below a vegetated hard rock cliff but has an embryonic sand dune also. L-album Wainscot was my target and I got 4 very quickly on the night. There were also a small number of migrants trickling in such as Turnip Moth Agrotis segetum and Pearly Underwing Peridroma saucia and with a background sound of Dark Bush Crickets calling, this was already a very fruitful session.
At 22.00 the excitement levels were cranked up several notches. A large noctuid landed on the side of the 125MV trap which superficially looked like a large Black-banded Polymixis xanthomista. I potted it and while trying to make sense of this, another similar one landed on the sand five minutes later. This was also quickly potted.
Black-banded was very much on my mind as I had accidentally found one at Galley Head, Co. Cork in 2010 and had plans to travel to Cork to re-find it a week or two later. So I was absolutely astonished that they could possibly have turned up here on the Wicklow coast…..potentially a bit of a mega given only 4 previous (Co. Cork only) records and fairly rare and local in the UK. This pair didn’t quite fit though, lacking the dark band and although not having a ruler, seeming much larger.
While looking at the illustrations of Black-banded and Feathered Ranunculus, Polymixis lichenea in the Field Guide to the Moths of GB and Ireland, I noticed that Large Ranunculus, Polymixis flavicincta was a better fit but I knew it hadn’t been recorded in Ireland. I had no mobile reception at the base of the cliff so couldn’t look up online photos to confirm my suspicions. At home, I was able to research further and took some wing measurements. The wing lengths of the two moths were 20 and 21mm putting them well outside the range of Feathered Ranunculus (15-18mm) and Black-banded (16-18mm). I circulated photos to some of the Irish experts but hardly anyone had experience of it. They were finally confirmed by Steve Nash of the UK in words like, “if they were taken in my garden, I would have no hesitation in calling them Large Ranunculus”. One was retained for Ken Bond to dissect and as a specimen for the Natural History Museum.
Although there were migrants on the move that night and normal wisdom would have concluded these Large Ranunculus were immigrants, I had my doubts. My suspicion was that they were of local origin given that two came within five minutes of each other to the light. These suspicions were confirmed when I trapped a further four at the same location 24 days later and a single another week later a little inland from the beach.
The distribution in the UK is southern but does extend all the way to the Welsh coast. I can’t find any mention of any major change in either distribution or abundance so I do wonder how long this little colony has existed at Arklow or if there are in fact others yet to be discovered. It uses a wide range of foodplants and habitats so can’t see why it shouldn’t spread from here.
30 June 2023