The BDS has obtained grants to carry out practical work for the Southern Damselfly in and around the Preseli SAC, which is one of its strongholds in both the UK and Europe. Grants have come from a variety of sources including Environment Wales, Wales Biodiversity Partnership and Pembrokeshire Biodiversity Partnership. The work has been carried out in partnership with Natural Resources Wales (NRW), Pembrokeshire Coast National Park Authority (PCNPA) and the Pembrokeshire Biodiversity Partnership.

Funding from NRW has enabled the BDS Conservation Officer to work on the conservation projects detailed on this page.

Generous funding has also supported the translation of some of the information on this page into Welsh. If you click on the Welsh titles, you will be taken to the text in Welsh and if you click on the English title you will be taken to the text in English.


Southern Damselfly Coenagrion mercuriale is the smallest of the ‘blue damselflies’ where the males are bright blue with black markings and the females are duller. Males can be distinguished from those of similar species by the ‘mercury’ mark on segment two of the abdomen and the spear-shaped markings on other abdominal segments. Females are usually dull green with the abdomen mainly black above. They have a thistle shape at the top of the abdomen and a few blue divisions between the segments near the tip of the abdomen. Rarer blue-form females can occur. Both sexes have a small lobe on the rear edge of the pronotum.

Wales page cons Southern Damselfly mercury mark Dave Smallshire

Wales page cons Gernos good habitat Claire Install

Habitat in Pembrokeshire

The species is rather sedentary, rarely flying more than 50 metres from its emergence site. This makes the species very vulnerable especially as it has very specialised habitat requirements. In Pembrokeshire, good condition breeding sites are within heathland and are flushes and shallow streams that are ground water-fed . This ensures consistently mild water temperatures and permanently flowing water. The streams have a gravely or clayey bed with patches of organic detritus. The watercourses should be well vegetated, but with areas of open water. Emergent water plants that mark suitable habitat include Bogbean Menyanthes trifoliata, Marsh St John’s Wort Hypericum elodes, Bog Pondweed Potamogeton polygonifolius and Fool’s Watercress Apium nodiflorum. The species also requires areas of nearby shelter for the adults.

Legal Protection

The Southern Damselfly in Wales is both a NERC Section 42 species (Section 41 in England) and a Biodiversity Action Plan species. It is protected in law under Schedule 5 of the Wildlife and Countryside Act 1981 (as amended) and is listed as Endangered on the Odonata Red Data List. Not only is it rare and endangered in Britain, it is also listed as Near Threatened on the European Red List and protected by the European Community Habitats and Species Directive. Its presence is a primary reason for the Preselis being designated as a Special Area of Conservation (SAC). It is therefore of paramount importance that the species key breeding sites in Wales are preserved, enhanced and expanded wherever possible.

Wales page cons Southern Damselfly in cop Dave Smallshire

Partnership Work

Since 2011 the British Dragonfly Society (BDS) has been working with partners in Pembrokeshire to both preserve and create important habitat areas for the Southern Damselfly. Two of these projects, at Penlan and Pensarn Corner, have been supported by Environment Wales with funding from the Welsh Government. Working in partnership with Natural Resources Wales (NRW – formerly CCW) and the Pembrokeshire Coast National Park Authority (PCNPA), British Dragonfly Society (BDS) staff and volunteers have created the ideal environment for the species at Penlan and saved a valuable area of habitat at Pensarn Corner. With other grant funding from the Wales Biodiversity Partnership, areas within a further stream on Brynberian Moor have been restored and a management plan for the Southern Damselfly within and near to the Preseli SAC has been drawn up. The management plan now informs and guides all the practical work carried out for the Southern Damselfly in this area.

The project in 2015 has been carried out with funding from NRW and in partnership with Pembrokeshire Biodiversity Partnership.

Wales page cons Waun Fawr 2June 2013 Claire Install


The Southern Damselfly was once more widespread in Pembrokeshire. Two of the three main populations have gone extinct, leaving small, scattered populations within and around the Preseli SAC which is also common ground. These are now vulnerable due to a large reduction in grazing, especially of larger stock. This lack of grazing has led to flushes becoming swamped and choked by adjacent vegetation, thereby making the habitat unsuitable for Southern Damselflies. Recent observations and several years worth of monitoring have shown that the population of Southern Damselfly in Pembrokeshire is declining and in many cases clinging on to the last fragments of habitat that are still suitable, but no longer ideal.

Recent changes in land management have put particular pressure on the existing populations in Pembrokeshire. The Southern Damselfly needs well-grazed and open vegetation beside small streams. It is also beneficial for the streams to have trampled margins and tussocks created by heavy grazing animals, like cattle or horses.

There are many constraints to achieving the correct grazing regimes for Southern Damselflies on common land. These constraints are due to economic, legal and cultural reasons. There are also many separate parties with an interest in common land, resulting in there being a number of individual issues to overcome before the practical problems can be considered and assessed. It is hoped that in future years we will be able to find a way to improve the grazing regime for the Southern Damselfly that is supported by and benefits all users of the common.