Leixlip Spa, Louisa Bridge in County Kildare is a site beside the Royal Canal about 1.5 km from the town of Leixlip. It is a Special Area of Conservation (SAC) and is fairly well known for having a number of plant and invertebrate species which are rare or locally uncommon in Ireland. Seepage from the spa has created a marsh with a couple of small ponds and the area is often alive with insects on a mild summers evening.
It was on such an evening, on the 10th July 2017 that I decided to visit with my net in hand. I made my way down through the site towards the ponds, netting and recording several different species of moth on the way. At the ponds I noticed some weakly flying whitish micro-moths flitting through the vegetation around the side of the waterbody. Individuals were often landing on the vegetation and none were travelling far. I netted a few for closer examination, releasing all but one, which I potted and kept to photograph. My initial impression was that I had an odd form of Brown China-mark Elophila nymphaeata, be it a little small and less robust. The following morning, in good light, I photographed the potted specimen but was still none the wiser as to its identity.
With the mystery still unresolved I returned to the site three days later, recording approximately 12 of these moths on the wing. I again netted a couple for closer examination, retaining a single specimen for photographing. Again the images taken did not conclusively resolve the puzzle and so on 17 July I uploaded the photographs to a Facebook Irish Moth Group.
Very quickly Eamonn O’Donnell suggested that Elophila rivulalis, a Continental species unrecorded in Ireland or for that matter Britain, could not be ruled out. Dave Allen sent images to some international experts who concluded that E. rivulalis was a likely candidate but that a specimen would need to be dissected to be fully sure. A specimen was duly sent to the Natural History Museum in London via Dave and eventually it was confirmed as this species. E. rivulalis is one of the Crambidae family and is closely related to the Brown China-mark. As it currently has no common/vernacular name I have proposed that it be called the Irish China-mark.
Repeated visits to the site throughout the summers of 2017 to 2019 have shown that it appears to be doing well with up to 40 seen in mid July 2017, up to 30 in early June 2018 and 38 to date in 2019. The flight season is from about late May to the beginning of August.