Southern Damselfly (Coenagrion mercuriale)
Species
Southern Damselfly (Coenagrion mercuriale). Male. Taken at Dry Sandford Pit, Oxon, on June 8th 2014. Approx 5x lifesize.
Male. Taken at Dry Sandford Pit, Oxon, on June 8th 2014.
(1/250th sec at f13. Approx 3x lifesize. Click image for larger version. © David Hastings)
Southern Damselfly (Coenagrion mercuriale). Male. Taken at Dry Sandford Pit, Oxon, on June 14th 2014. Approx 5x lifesize.
Male. Taken at Dry Sandford Pit, Oxon, on June 14th 2014.
(1/100th sec at f11. Approx 3x lifesize. Click image for larger version. © David Hastings)
Southern Damselfly (Coenagrion mercuriale). Female. Taken at Dry Sandford Pit, Oxon, on June 5th 2010. Approx 5x lifesize.
Female. Taken at Dry Sandford Pit, Oxon, on June 5th 2010.
(1/320th sec at f14. Approx 3x lifesize. Click image for larger version. © David Hastings)
Southern Damselfly (Coenagrion mercuriale). Mating pair. Taken at Dry Sandford Pit, Oxon., on June 11th 2018. Approx 5x lifesize.
Mating pair. Taken at Dry Sandford Pit, Oxon., on June 11th 2018.
(1/200th sec at f13. Approx 3x lifesize. Click image for larger version. © David Hastings)

Description

Wingspan: 30 - 40 mm; body length: 27 - 31 mm

The smallest blue damselfly, which has a very restricted distribution in Britain. The male's S2 marking typically resembles a head bearing a winged helmet (the so-called 'Mercury mark'). S3-6 are seldom more than half black, and there is always some blue at the base of S7. The female is dark and nondescript.

Its main strongholds in the UK are the New Forest, Dartmoor, Anglesey and the Preseli mountains in south Wales.

The Southern Damselfly only occurs in very specialised habitats. Favoured watercourses are base-rich, shallow and narrow, with shallow peat or silt over gravel and slow to moderate flows. They can be acidic or alkaline.

Eggs are laid into soft-stemmed submerged plants, and hatch after 4-6 weeks. Larvae develop over two years. The flight period is June and July.

Adults only fly in sunshine. Their flight is weak and low, and they stay close to the breeding site and do not appear to disperse easily to colonise new areas.

This a Red Data Book species, and a licence is required to handle it.

Sightings

12-Jul-2018 : Parsonage Moor, Oxon (9m,3f)
12-Jul-2018 : Cothill Fen, Oxon (3m)
15-Jun-2018 : Dry Sandford Pit, Oxon (6)
11-Jun-2018 : Dry Sandford Pit, Oxon (3m,1f)

14-Jun-2017 : Dry Sandford Pit, Oxon (1m)
03-Jun-2017 : Dry Sandford Pit, Oxon (1m,1f)

09-Jul-2016 : Dry Sandford Pit, Oxon (1f)
28-Jun-2016 : Dry Sandford Pit, Oxon (1m)

12-Jul-2015 : Parsonage Moor, Oxon (1m)
02-Jul-2015 : Dry Sandford Pit, Oxon (1m)

28-Jun-2014 : Dry Sandford Pit, Oxon (2)
14-Jun-2014 : Dry Sandford Pit, Oxon (6m,2f)
08-Jun-2014 : Parsonage Moor, Oxon (4m)