The northern emerald (Somatochlora arctica) is a species of emerald dragonfly found in northern and middle Eurasia. The species was first described in 1840 from Scandinavia. It is a relatively small dragonfly, just long, and is recognizable by its hairy thorax, dark abdomen, and bright green eyes. The males have narrowly waisted abdomens, while the females have straight ones; the females are also recognizable by the two lateral yellow spots behind the thorax. Northern emeralds pass two years as larvae in sphagnum-rich bog pools before emerging as adults which hunt above peat bogs, wet meadows, and open woodlands. Despite being assessed as a least-concern species by the IUCN, northern emeralds are threatened by habitat loss caused by human activity, and climate change is expected to exacerbate the problem. The northern emerald is found from Japan and the Kamchatka Peninsula through much of Russia. It is abundant throughout Fennoscandia, and is also well-known from the Alps and the Scottish Highlands. Its distribution in lowland Europe is sparse, but the dragonflies can be hard to find and record.
Taxonomy The northern emerald is known scientifically as Somatochlora arctica and is placed in the family Corduliidae. The genus Somatochlora, known as the "striped emeralds", includes 42 species found across the Holarctic realm. It is the largest genus of the family Corduliidae.The binomial name comprises two parts: the genus name, Somatochlora, is composed of the Greek-derived prefix somato- ('body') and adjective chlorus, used in taxonomy to mean 'green'. The species epithet is derived from the feminine form of the Latin arcticus, meaning 'northern', or, indeed, 'arctic'.
Taxonomic history The northern emerald was first scientifically described under the name Aeschna arctica in 1840 by Johan Wilhelm Zetterstedt. Zetterstedt provided a brief physical description and wrote he had discovered the dragonfly in August of 1821, noting it was found in sub-alpine parts of Finland and Norway. The original description was published in his thousand-page work Insecta Lapponica, a description of the insects of Lapland intended to supplement Linnaeus' Fauna Svecica of nearly a century before.
The very same year as Zetterstedt published his description, Belgian aristocrat and entomologist Edmond de Sélys Longchamps – considered a "founder of odonatology" – described a species he called Cordulia subalpina from Belgium. In a paper in the journal Bulletins de l'Académie Royale des Sciences et Belles-Lettres de Bruxelles he described a species, discovered in June 1840 by Monsieur Putzeys, a Crown prosecutor in Arlon. He noted it was similar to Somatochlora alpestris (then called Cordulia alpestris).
Ten years later, de Sélys published a comprehensive book, Review of the Odonates or Libellules of Europe, in which he gave Zetterstedt credit for ths species, listing his own Cordulia subalpina as a junior synonym. However, he did reclassify Zetterstedt's species into the genus Cordulia, producing the new name Cordulia arctica. Sélys also provided a detailed physical description and described its distribution: Belgium, Norway, Sweden, Finland, and, thanks to a specimen recorded by a Mr. Weaver, Scotland.
In 1871, de Sélys published Synopsis des Cordulines and classified it in the subgenus Epitheca. He returned in 1887 to finally reclassify it in into Somatochlora, noting its range as cold and temperate Europe, Siberia, and Transcaucasia. Sélys died in 1900. In 1909, Russian zoologist Aleksandr Bartenev described a new species, Somatochlora gratiosa, from Siberia. This species would stand as an accepted taxon until 1958 when Japanese entomologist Syoziro Asahina synonymized it with S. arctica.
Phylogenetics Classification within the genus Somatochlora was traditionally based on physical characteristics, especially of the nymphs, the wing venation, and the morphology of the anal appendages . However, these characteristics "are highly prone" to convergent evolution, making genetic-based research necessary to work out the true evolutionary relationships between species. A 2025 paper published in the journal Systematic Entomology did just that. The phylogenetic tree their research suggested that Somatochlora arctica was most closely related to a clade comprising Somatochlora franklini, S. forcipata, S. dido, and S. incurvata. However, the exact placement of the species was unresolved and contradicted previous analyses. Their research also found that S. arctica, S. franklini and S. incurvata had all likely diverged approximately five million years ago, in the end of the Miocene epoch – the most recent divergences within the genus.
Description
Members of the genus Somatochlora are generally medium-sized dragonflies with metallic green to black colouration and bright green eyes. Northern emeralds (Somatochlora arctica) are smallish dragonflies with dark abdomens and lighter, hairy thoraxes, usually measuring from long and a wingspan of around . The colour of the abdomen is blackish, while the head and thorax are bronzey green. Females have two characteristic oval yellow spots on the abdomen next to the thorax, similar to spots on brilliant emerald females. Both sexes have characteristic yellow spots on their faces next to the eyes, which are bright green in mature individuals.
Northern emerald wings are not completely clear but rather are "suffused with a yellowish tint" which becomes strongest close to the leading edge of the wing. The base of the wings is also pale ochre, especially the male inferior wing. Populations of the dragonflies in west Siberia, particularly in bogs on the Vasyugan Plain, exhibit wings "smoked" with amber-brown. A similar phenomenon has been recorded in Somatochlora flavomaculata specimens from the same area. The pterostigmata – pigmented spots on the front corners of each wing – are black-brown in males and dark brown in adult females, paler brown in immature ones. The accessory membrane, a small membrane at the base of the wing next to the thorax considered useful for identification, is white in both sexes, but narrower in the female. The legs are mixed black and brown in colour. The male legs are more predominantly black, with only one side of the first femur (third segment) brown; the females are more so, with all the femurs being brown.Males are distinctive because the two segments of the abdomen closest to the thorax, and the base of the third, are enlarged such that the dragonfly superficially appears to have a long thorax and a shortened abdomen. The abdomen has a narrow waist and then widens again, being widest in the middle. Females have abdomens without a narrowed waist: seen from above, they are a rectangular shape, tapering gently towards the top.
The tip of the final, tenth segment of a dragonfly abdomen carries a set of short appendages. Both sexes have an upper pair called cerci or upper anal appendages but males additionally have a pair of lower appendages called the epiprocts. In females, the upper appendages are small and "leaf-like". The male upper appendages are rather long and shaped like calipers; the epiprocts are smaller, short, triangular, and slightly curved. The female's vulvar scale – an organ possessed by some dragonflies similar to an ovipositor "used to 'throw' eggs rather less precisely" – is "triangular, pointed, and spout-like." It departs the abdomen at about a 30° angle and is a little longer than the ninth abdominal segment.
Northern emeralds are physically similar to alpine emeralds, Somatochlora alpestris, and must be distinguished mainly on the basis of the morphology of the anal appendages. The physical similarity lead to the two species being traditionally grouped together. However, the 2025 phylogenetic study noted that the physical commonalities used to group S. arctica with S. alpestris were often subject to convergent evolution. Their molecular study found this classification incorrect, with S. arctica and S. alpestris belonging to quite different groups within the genus.
Reproduction and development
Northern emeralds mate in what is called the "wheel formation". First, using the appendages on the tip of his abdomen, the male grasps the female behind the head: this is called the "tandem formation". The male leads the female into the tree canopy. She then curls her abdomen to the male's secondary genitalia, which are located on the underside of his thorax. By this means the female's eggs are fertilized. Mating takes up to an hour. Once it is done, the female leaves to deposit her eggs alone. (In some dragonfly species, the male guards the female while she does this.) Usual oviposition sites are small pools closely protected by vegetation, such as in clumps of underwater sphagnum moss.
The larva is the "main life stage" for the northern emerald dragonfly, and it lasts at least two years. Northern emerald larvae are distinctly hairy creatures, and moult several times during their development. The larval abdomen has no spines on the back or sides, unlike some other Somatochlora species, and the hind-leg's third and longest segment (femur) is relatively short, reaching only as far as the abdomen's sixth segment. The larva's "mask" – actually the prehensile lower lip, extended to catch prey – has numerous somewhat shallow crenations, each sprouting five bristles. They are squat, and their longish legs give them a spider-like appearance. A mature larva is usually between long, or less than half the size of the adult. Between May and June, mature larvae clamber out from the water and onto the stems of nearby plants such as sedges. Over the process of two hours, the adult dragonfly emerges, leaving behind an exuvium: the larva's last skin. The callow then takes a short "maiden flight", usually into available woodland canopy. Several days can pass before the callow develops its mature colouration. The adults only live for eight weeks – or fewer.
Behaviour and activity Though they are most often seen in July, the northern emerald flight period generally extends from late May to the middle of September. Northern emeralds are swift predators who hunt in and around bog habitats, usually flying rather low. The males patrol potential breeding grounds and search for females, but generally don't linger in one area long. The males are aggressive and frequently come into conflict. Two rivals will soar up to above the bog before dropping rapidly, flying circles tightly around each other and then separating.
Kenneth Morton described their flight habits in Austria thus in a 1928 paper:They flew as a rule only a foot or two above the herbage, an almost stationary hovering flight alternating with short darting forward movements; only once a higher, more joyous looking, flight was noted when the atmospheric conditions were stiller (not to be confused with the high, backwards and forwards flight of adolescent examples in sheltered sunlit places in the woods, or the occasional extended rapid flights which are probably of an exploratory nature). Habitat
The northern emerald is regarded as a "bog specialist". The larvae develop and hunt in bog pools, especially among waterlogged sphagnum moss; adults can be found flying around bogs, in wet meadows and heaths, open woodlands, and lightly treed moors. Early 20th century observations made by Kenneth Morton in the Austrian Tyrol reported them to be found abundantly in wet meadows there.