73.010 Dewick’s Plusia, Macdunnoughia confusa – New to Ireland

The night of 7th/8th Oct 2023 was warm and overcast with moderate southerly winds emanating from the Bay of Biscay. As a birder, I associate such winds in October with the arrival to Ireland of European birds blown off course on their autumn migrations. As a very recent moth-er (I only started ‘mothing’ in June 2021), I’ve also learned that such conditions are also perfect for the potential arrival of European moths to Ireland.

Our home is situated just south of Newcastle, Co. Wicklow (O20) and lies 1.5km inland from the coastal wetlands that run south from Five-Mile-Point to Killoughter. Our garden is a little over an acre in size and, over the past ten years, we’ve planted over 250 natives trees and a wildflower meadow, as well as creating a pond. A section at the back of the garden is left totally wild with brambles, ferns and nettles. I do almost all of my trapping in our garden and, since starting to trap in June 2021, I’ve recorded approximately 400 moth species… so the effort of creating this wildlife garden has certainly paid off.

Inspired by the fact that Angus Tyner’s garden (which lies just south of our place) had become ‘Clifden Nonpareil Central’ over the previous week, I set up my Double 20W Actinic Skinner trap in the back of the garden more in hope than expectation. For good measure, I also put my first (and very basic) 20W Actinic Skinner on the front porch of the house. Often the white wall of the house can host more moths than this particular trap holds. A final check of the traps at midnight revealed my very first Merveille du Jour Griposia aprilina on the house wall. I felt that after seeing this beauty, anything else would be a bonus.

I closed up the porch trap and collected the Double 20W Skinner in darkness, early on the morning of 8th Oct (before my nemesis of our resident Robin had even stretched a wing). It was obvious that there wasn’t big number of moths in either trap. However, looking into my main trap I noted a Gold Spot Plusia festucae, a Silver Y Autographa gamma and my first Black Rustic Aporophyla nigra of the season. As it got brighter, I started extracting the egg cartons from my main trap. As I removed my 4th egg carton, I found myself looking at a moth I had never seen before.

It was Silver Y in shape but considerably smaller. The main colour was orange-brown on the head and thorax (with two distinct orange-brown ‘tufts’) and greyish-brown along the lower section of the forewing (the leading edge area) . However, the most striking feature was a narrow silver-white line which extended from the base of the forewing along the mid-forewing section before sweeping upwards into a larger ‘dog leg’ shape. Part of the upper section of the forewing was a glistening orange-brown. The crossband was greyish brown with a narrow pale grey and orange-brown edge to the tip of the forewing.

I took some record shots and placed the moth into my holding box before setting out to attempt to identify what species I had just trapped. My main resource is the Waring/Townsend/Lewington guide and, as I started checked the Silver Y-type groups, I found myself looking at Dewick’s Plusia Macdunnoughia confusa. It seemed to match what my moth was. I then checked the ‘atlas’ which revealed that Dewick’s Plusia doesn’t occur in Ireland and that, even on the southern coast of England, it is a relatively scarce European migrant species. So I counted it out of the equation and went back to the guidebook. Perhaps it was one of those small ‘gammina’ forms of Silver Y?

No matter how hard I searched, I kept coming back to Dewick’s Plusia. I then put my record shot through ‘Obsidentify’ and found myself shaking a little (a lot!) when it came back with a 100% positive identification as Dewick’s Plusia! Could it be possible that I had found such a rare moth species in our garden? Still in denial, I sent the images to Michael O’Donnell and Angus Tyner. Those few moments waiting for their reaction was like a rugby referee speaking with the TMO saying ‘the on-field decision is a Dewick’s Plusia….is there any reason why I can’t award a Dewick’s Plusia?’

The response from both came back very quickly with a huge congratulatory and excited confirmation that the moth I had in my holding box was indeed a Dewick’s Plusia! This was shortly followed by both guys messaging with a confirmation that it was a new moth species for Ireland.

Late that afternoon, I released the Dewick’s Plusia in the garden. It didn’t stay long enough to get a ‘more natural’ image as it kicked into action within seconds and headed off south. I never thought when I set out on my mothing journey that I’d record a first for Ireland. So, as mad as it might sound, watching it fly off, I thanked it for gracing me with its presence and for making 8th Oct 2023 a mothing day I will never forget.

Many thanks to both Michael and Angus for their help that morning, and to Jim Fitzharris who dropped in (twitched) to share the excitement of finding this jewel of a moth.

Eric Dempsey

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