Description

Rare, weak flying Damselfly.

Male: blue and black with a distinctive ‘mercury’ mark on segment 2 near the top of the abdomen.

Female: black with green markings.

 

Where to See

Latin NameCoenagrion mercuriale
Habitat

In the UK the Southern Damselfly is primarily a species of base-rich runnels and streams often within acid heathland areas. However, it also occurs on water meadows in the flood plains of two chalk rivers, a habitat said to be more typical of many continental sites. At breeding sites the water is typically shallow and slow-flowing over a gravel or marl bed with patches of organic detritus. It may be that a more or less constant, relatively high, water temperature in winter in the spring-fed sites is particularly important in determining site suitability.

Threats

The main factor thought to be influencing the decline of the species is the removal of grazing animals that maintain the open nature of the species’ breeding sites. Other potential threats are abstraction of water, leading to a lowering of the water table, drainage due to agricultural and forestry pressures, and excessive nutrient enrichment from the runoff of nitrogenous fertilisers from adjacent agricultural land. Isolation and scarcity of habitats is a cause for concern.

Status & Distribution

The Southern Damselfly is a rare species in the UK as it is living on the extreme north-western fringe of its European range. Its two main strongholds are in the New Forest, Hampshire and the Preseli mountains, Pembrokeshire. Smaller colonies are found in Devon, Dorset, Anglesey, Gower, Oxfordshire and on the flood plains of the Test and Itchen rivers in Hampshire. There are old records from Cornwall and Somerset and elsewhere in Devon, Dorset and South Wales. The range of the species has contracted in the last thirty years.

 

Similar Species

Easily confused with the other members of the genus Coenagrion, such as Common Blue Damselfly.

Look for

  • Short pterostigma (wing spots) with dark centre.
  • Thin blue antehumeral stripes on the thorax.
  • Coloured line between eye spots.
  • Flat base to the median lobe.
  • Male: distinctive ‘mercury’ mark on segment 2 near the top of the abdomen.
Management

Protected under Schedule 5 of the 1981 Wildlife and Countryside Act.

Listed in Appendix II of the Berne Convention and Annex II of the EC Habitats Directive.

10 SACs support Southern Damselfly.

Ecology of the Southern Damselfly publication

Biodiversity Action Plan priority species

Species Action Plan

Species GroupDamselflies
Identification Notes
  • Length: 29-31mm
  • Short pterostigma (wing spots) with dark centre.
  • Coenagrion spur on the side of the thorax.
  • Small coloured line between the eye spots.
  • Thin blue antehumeral stripes on the thorax.
  • Male: Blue with black markings including distinctive ‘Mercury’ shape on segment 2 near the top of the abdomen.
  • Female: Black with narrow green patterns on abdomen.
  • Weak, low flying.
Flight PeriodSouthern Damselfly
Larval Information

The larvae are distinctive in that they have very small, unpatterned caudal lamellae.

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