Red-eyed Damselfly (Erythromma najas) is a scarce and localised damselfly in Monmouthshire, found at only a few sites. Prior to 2017 it was the only Erythromma damselfly in the county but since then, its relative, Small Red-eyed Damselfly (E. viridulum) has colonised and may now be the more common of the two species.
The oldest record we have in our dataset is from Coity Tips, Blaenavon on 11 August 2007 (observer Steve Williams).
Current distribution in the county: what we know
Post-2019 records come from just six widely separated sites: the River Wye at Bigsweir Bridge, Magor Marsh, Uskmouth nature reserve, Tredegar House lake and Cwm Hedd to the west of Newport, and the Monmouthshire and Brecon Canal at Sebastopol.
Current distribution in the county: what we don’t know
Prior to 2020, in addition to the Coity Tips record, Red-eyed Damselfly was recorded from the following additional sites, all in the south of the county, and it would be valuable to know if it is still present at any of these (year of most recent record in brackets): Ynys-y-fro Reservoirs (2019), Lliswerry Pond (2018), Mathern fishing ponds (2017), Goldcliff lagoons (2014), Rogiet country park (2013) and Dewstow garden in Caldicot (2011). It is possible that records from a small number of these sites relate to Small Red-eyed Damselfly, which is now found at several of them, and may not have been ‘on the radar’ of the observers at the time.
There is a 2018 record from the River Wye at Monmouth, and searches here and at other sites along the Wye will help in establishing the extent of its distribution on the river, and to assess the effect that ongoing severe agricultural pollution is having there. Although there are no records from the Usk it is possible that the species occurs there too. It was recorded in 2016 on the Cwmbran stretch of the Monmouthshire and Brecon canal and searches here and along other sections of the canal would be useful to confirm the extent of its population on that waterbody.
Red-eyed Damselfly is uncommon in Wales, where we are on the western edge of its British distribution: it mainly occurs in southern counties west to Carmarthenshire, with another population on the Severn from Newtown to the English border, and a few sites in far northeastern parts of the country. It is widespread in England as far north as Yorkshire, but is absent from Scotland. Elsewhere in Europe, it is found from France east to Russia, north to Scandinavia and Finland, and south to northern Italy and the Balkans; it is also found throughout Asia east to Japan.