Northern emerald (Somatochlora arctica)

Description

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Northern emerald fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Northern emerald description

The northern emerald (Somatochlora arctica) is a fast-flying dragonfly of the Corduliidae family ⁽³⁾, commonly named emerald dragonflies due to their characteristic metallic-green colouration ^{(2) (4)}. There is a yellow spot on each side of the bronze-green head, as well as yellowish mouthparts and emerald green eyes ⁽³⁾. The thorax is metallic-green and covered in thin, yellow hairs, and the wings are slightly orange-yellow in colouration ⁽³⁾.

The abdomen of the male northern emerald is slimmer than in the bulkier female. The female also has two dull yellow spots on the third segment of the abdomen and light rings around the first two joints. The first two segments of the male’s abdomen are suffused with yellow along the sides. The male also has two pincer-like extensions at the base of the abdomen ⁽³⁾, used to grip the female during copulation ⁽²⁾.

The larvae of the northern emerald have bulky bodies ⁽⁴⁾, with a short abdomen, the upperside of which is covered in small hairs ⁽³⁾.

Size

Abdomen length: 3.7 - 4 cm ⁽²⁾

Wingspan: 6.8 - 7 cm ⁽²⁾

Larva length: c. 0.2 cm ⁽³⁾

Northern emerald biology

It can be assumed, as with all dragonfly species, that the northern emerald is a highly skilled predator. It detects its prey mainly by sight, congregating quickly in areas where prey is abundant, such as at a termite nest or beehive. All dragonflies are opportunistic and generalised predators, with small flying insects being the primary component of their diet ⁽⁷⁾.

The flight period of the northern emerald is between mid-May and September ⁽²⁾. Throughout this period, the male defends a territory around the edges of its chosen water body ⁽³⁾. Copulation takes place when a female dragonfly enters this territory, when the ‘wheel’ position is adopted, with the male grasping the female’s head with the claw-like appendages at the base of the abdomen. Egg laying in all dragonfly species follows shortly after copulation ⁽²⁾, with the female northern emerald laying the eggs alone, placing the tip of the abdomen below the Sphagnum moss at the surface of the peat bog or swamp ⁽³⁾.

All dragonfly larvae have a ‘mask’, which is an extendable structure that has strong hooks to grip prey and is retracted back to the mouth to eat it ^{(2) (7)}. The larvae of the northern emerald burrow into the Sphagnum moss ⁽²⁾, and emerge to metamorphose into the adult form after two years of development ⁽³⁾.

Northern emerald range

The distribution of the northern emerald is centred around Scandinavia, with its range including Sweden, Finland and Norway ⁽⁵⁾. The northern emerald also occurs in Belgium, the Netherlands, Germany, France, Poland and the mountainous regions of Scotland and Ireland ⁽⁶⁾.

Northern emerald habitat

The northern emerald lives around slowly moving water bodies such as peat bogs and swamps ⁽²⁾, especially in areas where the vegetation is dominated by Sphagnum moss ^{(2) (6)}. The larvae are found beneath the leaves and moss on the surface of their aquatic habitat ⁽⁴⁾. The adult northern emerald can be found up to elevations of 2,000 metres in the southernmost parts of its range ⁽²⁾.

Northern emerald status

The northern emerald has yet to be globally assessed, but is classified as Near Threatened (NT) on the IUCN Mediterranean Red List ⁽¹⁾.

Northern emerald threats

The threats to the northern emerald are unknown, but it can be assumed, as with all dragonflies, that loss of breeding sites due to draining and infilling may be a major threat. Land used by dragonflies for feeding, roosting and sheltering has also been lost, and pollution and eutrophication are threats to the remaining suitable habitats and breeding grounds ⁽⁷⁾.

Northern emerald conservation

There are currently no specific conservation measures known to be in place for the northern emerald.

Find out more

More information on invertebrates and their conservation:

• Buglife:
  http://www.buglife.org.uk/

More information on dragonfly and damselfly conservation:

• Moore, N.W. (1997) Dragonflies: Status Survey and Conservation Action Plan. IUCN/SSC Odonata Specialist Group, IUCN, Gland, Switzerland and Cambridge, UK. Available at:
  http://data.iucn.org/dbtw-wpd/edocs/1997-042.pdf

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Glossary

Abdomen

In arthropods (crustaceans, insects and arachnids) the abdomen is the hind region of the body, which is usually segmented to a degree (but not visibly in most spiders). In crustacea (such as crabs), some of the limbs attach to the abdomen; in insects the limbs are attached to the thorax (the part of the body nearest to the head) and not the abdomen.

Eutrophication

A process in which a water body is enriched with excessive nutrients (such as nitrogen and phosphorus) resulting in the excessive growth of aquatic plants and the depletion of oxygen, creating unfavourable conditions for other organisms, such as fish.

Larva

Immature stage in an animal’s lifecycle, after it hatches from an egg and before it changes into the adult form. Larvae are typically very different in appearance to adults; they are able to feed and move around but are usually unable to reproduce.

Metamorphosis

An abrupt physical change from the larval to the adult form.

Territory

An area occupied and defended by an animal, a pair of animals or a group.

Thorax

Part of the body located between the head and the abdomen in animals. In insects, the three segments between the head and the abdomen, each of which has a pair of legs. In vertebrates the thorax contains the heart and the lungs.

References

1. IUCN Mediterranean Red List (November, 2011)
   http://ww.iucnredlist.org/initiatives/mediterranean
2. Gibbons, B. (1986) Dragonflies and Damselflies of Britain and Northern Europe. Hamlyn Publishing Group, London.
3. McGeeney, A. (1986) A Complete Guide to British Dragonflies. Jonathan Cape Limited, London.
4. Brooks, S. (2002) Dragonflies. The Natural History Museum, London.
5. Procter, D. and Harding P.T. (Eds.) (2005) Red Lists For Invertebrates: Their Application at Different Spatial Scales - Practical Issues, and Pragmatic Approaches. JNCC Report, Peterborough, UK. Available at:
   http://jncc.defra.gov.uk/PDF/jncc367_web.pdf
6. Knijf, G.D., Flenker, U., Vanappelghem, C., Manci, C.O., Kalkman, V.J. and Demolder, H. (2011) The status of two boreo-alpine species, Somatochlora alpestris and S. arctica, in Romania and their vulnerability to the impact of climate change. International Journal of Odonatology, 14: 111-126.
7. O’Toole, C. (2002) The New Encyclopedia of Insects and Their Allies. Oxford University Press, Oxford.