Southern damselfly  (Coenagrion mercuriale)

Classified as Near Threatened (NT) on the IUCN Red List 2006 (3), and Rare under the GB Red Data Book. Listed under Appendix II of the EC Habitats Directive and Annex II of the Berne Convention (4).

Males are sky-blue and black in colour, with blue eyes and two small eyespots. They can be distinguished from the males of similar species by the blue 'mercury mark' on the second segment of the abdomen, but detailed examination of the anal appendages is the only reliable method. Females do not possess these anal 'accessory genitalia' but have an ovipositor, which is not always easily visible (5). Females are generally green or blue and slightly lighter than males in colour, becoming brown as they age. They tend to have similar markings to males on the head and thorax but have darker abdomens. In both sexes the wings are clear with small black marks towards the tips (6).

This globally threatened species (4) is found in Western Europe and Northwest Africa, and is mainly centred on the western Mediterranean. In Great Britain it reaches the north-western extreme of its range (7), and is largely restricted to the south west with two strongholds in the New Forest and Pembrokeshire. It is also found in Devon, Dorset, Mid-Glamorgan, Oxfordshire, Hampshire, the Gower Peninsula, and Anglesey (4).

You can view distribution information for this species at the National Biodiversity Network Gateway.

The southern damselfly breeds mainly in heathland streams as well as chalk streams and calcareous mires (4).

Increasingly more is known of the biology of this species as a result of research initiated by the UK southern damselfly Species Action Plan Steering Group (2). Adults can be seen flying between mid-May to August (7), the flight is weak, and they tend to stay level with grasses and other vegetation (8). As with all odonata (dragonflies and damselflies), males and females fly linked together in tandem whilst mating, forming the 'wheel position' (8). When female southern damselflies lay their eggs, they often remain in tandem with the male and drag him below water where the eggs are laid on submerged or emergent vegetation (2). The larvae, which are voracious predators, hatch soon after the eggs are laid, but development to the adult stage takes 2 years (8).

Since 1960 the UK range of this species has decreased by 30% (4). Reasons for this decline include a decrease in grazing levels resulting in a loss of the open habitat needed at breeding sites. Water drainage, dredging and nutrient enrichment from agricultural run-off are also likely to have impacted on this species (7).

The UK population of the southern damselfly is of international importance. The species was highlighted as a priority for conservation by the UK Biodiversity Action Plan (UK BAP). The Species Action Plan has three main aims: to ensure that all UK populations are in favourable condition, to maintain the 1995 UK range preventing further loss of sites in England and Wales, and to increase the 1995 range by encouraging re-establishment of 5 former sites in 2005 (4). A steering group was formed to co-ordinate the conservation of this species; this includes the Environment Agency, The Wildlife Trusts, English Nature, Countryside Council for Wales, the British Dragonfly Society and Liverpool University (7).

There may be further information about this species available via the National Biodiversity Network Gateway.

The UK Biodiversity Action Plan for this species is available at UK BAP.

View information on this species at the UNEP World Conservation Monitoring Centre.

See the website of the British Dragonfly Society:
http://www.dragonflysoc.org.uk