Somatochlora metallica
Somatochlora metallica (Vander Linden, 1825)
Local names: Brilliant emerald, Glänzende Smaragdlibelle, Metaalglanslibel, Cordulie métallique, Metalltrollslända
Species Information
Description
Together with S. meridionalis it is the largest species of the emeralds. The body is entirely bright green except for two yellow spots at the base of the abdomen and a yellow U-shaped band across the frons. The band can sometimes be narrowly separated at the middle. In the females, the distinctive character is the long vulvular lamina at right angle to the abdomen. It can be distinguished from S. meridionalis by the pterostigma which is (usually) light brown instead of black and by the absence of yellow spots on the side of the thorax. The waist is narrow but the abdomen is less clubbed than Cordulia aenea, being widest at S6-S7.
Size
Habitat
Somatochlora metallica occurs at stnding and slow-flowing waters, which may be partially or nearly completely shaded. Lowland and mid-elevation localities are often in forested or semi-forested areas. Suitable habitats include mostly standing waters such as lakes, ponds, large pools and open water in fenland and Sphagnum peatbogs. More rarely the species is found at slow-flowing to moderately swift streams and rivers., as well as man-made canals. Most habitats have a bank vegetation of trees, high reeds or Sphagnum rafts, with stretches of open water without vegetation. The water is generally over a meter deep and bottom sediments are rich in organic detritus and often muddy. In the highest European mountains, the species extend beyond the tree line and is well established in a number of lakes and large open bogs. It is present in low numbers in the tundra landscape of northern Fennoscandia, north of the taiga. The species has a wide altitudinal range and in temperate Europe it occurs from the lowlands up to 2 400 m. However, it is most common at middle elevations, with for example 70 percent of Swiss recordings coming from around 600 m. In the south of its range, the species becomes progressively more restricted to higher altitudes, being confirmed to mountain lakes between 850 m and 2 350 m in Spain and the Balkans.
Distribution
Somatochlora metallica is common throughout most of Europe and reaches well north of the Arctic Circle. It is rare or absent in the Mediterranean area and the lowlands of the Baltic Peninsula. It is also absent from Ireland and occurs only at two, small disjunct areas in Great Britain, one in Scotland and the other one in south-east of England. To the south, it reaches the Pyrennes, both on the French and the Spanish sides, and the north of Italy. In south-east Europe it is confined to mountain lakes in Romania, Bosnia and Herzegovina, Montenegro and Bulgaria and is replaced by S. meridionalis at runnig water s in the lowlands. The situation in Hungary, where both species occur, is unclear.
Flight Period
June to September
Behavior
Males patrols along shorelines, preferably in shaded areas in lowlands but in full sunshine at mountain lakes. It often flies higher and further from the shore than Cordulia aenea, and takes fewer hovering stops. Patrolling males are aggressive and battles other males frequently. Immature males can be found far from water, in glades, open scrubs or adjacent meadows. Mating, resting and foraging is done in nearby trees or shrubberies. Females oviposit by repeatedly hammering the end of the abdomen against the wet ground near the water or in floating vegetation. Larvae live in bottom material under overhanging trees or in other shaded areas. Development of the larvae takes at least two years. Exuviae is found in vegetation close to the water or a bit further away on bridges, towed boats, stoneworks or such.
Conservation Status
Similar Species
Somatochlora meridionalis, Cordulia aenea, Somatochlora alpestris, Somatochlora arctica
External Links
Genus: Somatochlora
Somatochlora, or the striped emeralds, is a genus of dragonflies in the family Corduliidae with 48 described species found across the Northern Hemisphere. This is a large genus, especially in North America from where the not so apt name 'striped emeralds' originates, and the only corduliid genus with more than a single species in Europe.
Identification Diagnosis
Somatochlora are medium-sized dragonflies, with largely dark bodies that have a metallic green lustre. Eyes are reddish brown at emergence, but becomes brilliant green. Frons are dark metallic green with yellow spots on both sides.
Abdomens of males generally have a diagnostic shape (exept S. borisi who more resemble a *Cordulia). S1-S2 is bulbous, S3 is waisted, S4-S10 gradually widens up to about halfway, around S6-S7, and then gradually narrowes. They are not clubbed near the end. The abdomen is dark green to almost black, with minor yellowish markings on the sides. Male appendages are rather long, often with upcurled tips and several irregular ventral teeth. Lower appendage is triangular, with a narrow, upcurved tip. Female appendages are very long. Their vulvar scale is large, visible when viewed from the side, often shaped like a spout or trough, and distinctly projecting in most species.
Separation from other genera
Both Cordulia and Oxygastra have a uniformly dark frons, the male of these genera has a conspicuously clubbed abdomen, with S7 and/or S8 widest, and a deeply notched lower appendage. Their females have inconspicuous vulvar scales. Moreover, Cordulia has only one cross-vein between the hindwing triangle and base (not two) and Oxygastra has deep yellow streaks down the middle of the abdomen.
Separation of the species
The seven species found in Europe may be most easily determined in the hand by the shape of the anal appendages in males and by the vulvar scale in females. The patterns of yellow spots on the face, thorax and abdomen are also distinctive features.
Behaviour
Male patrols are swift and often stealthy or erratic. Females are especially shy, but may be detected by the rustling of wings while ovipositing alone under the cover of dense vegetation. Both sexes rarely perch near the waterside, but rather up in trees.
Family: Corduliidae
The Corduliidae, also knowns as the emeralds, emerald dragonflies or green-eyed skimmers, is a family of dragonflies. These dragonflies are usually black or dark brown with areas of metallic green or yellow, and most of them have large, emerald-green eyes. The larvae are black, hairy-looking, and usually semiaquatic. They are not uncommon and are found nearly worldwide. The Treeline Emerald (Somatochlora sahlbergi) belongs to this family and is not (yet) rare but considered extremely hard to see as an adult. It is one of the species most endangered by the global warming.