Somatochlora alpestris
Somatochlora alpestris (Selys, 1840)
Local names: Alpine emerald, Alpen-Smaragdlibelle, Taigaglanslibel, Cordulie alpestre, Fjälltrollslända
Species Information
Description
Somatochlora alpestris is rather small and robust, has a dark green, almost black-green, body with bright-green eyes. It can be distinguished by a white, not yellow, ring between S2 and S3 and by the presence of two cubito-anal cross-veins in the fore wings, where similar species has only one. On the males, the appendages are distinctive, convergent and doubly angled. The vulvular lamina of the females is large, reaching halfway along S9, triangular in shape and projecting at a right angle to the abdomen's axis. Frons is black with small yellow spots on each side. These are the only yellow markings on the body. The contrast between the eye and body colour is greater than on S. metallica or C. aenea. Pterostigma are dark or orange, where S. sahlbergi has lighter colouration.
Size
Habitat
Somatochlora alpestris favours flooded depressions in peat bogs, small peaty ponds and man-made peat diggings in Sphagnum bogs and transitional mires. More seldom, it is found in larger acidic peaty waters in open alpine meadows, semi-wooded areas or coniferous forests. The species is confined to cold arctic and mountain climates. The larvae are well adapted to these conditions, as they are tolerant to freezing in winter and desiccation of the peat layers in which they live in the summer. Conversely the adults show a great sensitivity to summer weather conditions, being decimated by summer snowfalls lasting longer than three or four days.
Distribution
Somatochlora alpestris is, together with Aeshna caerulea, one of the best examples of a dragonfly with a boreo-alpine distribution. It is widely distributed in Fennoscandia and (probably) the north European Russia, and is reasonably common throughout the higher parts of the central European mountains. In Fennoscandia it occurs from sea level in the north to more mountainous areas in the south. In central Europe, it is confined to to mountain ranges from 800 m (rarely as low as 600m) to ca 2 500 m. It is widespread and generally common in the Alps but is less frequent in other mountain ranges. Other inhabited mountain ranges include, the Vosges in France, the Fichtelgebirge, Erzegebirge, Thuringian forest, Harz and Black Forest in Germany, the Tatra and the Carpathian Mountains in the Czech Republic, Poland, Slovakia, Ukraine and Romania. Recent studies has shown the species to be more common in the Carpathian range than previously thought.
Flight Period
June to early-August in the north, early September in the south.
Behavior
Somatochlora alpestris is hunting in sunlit glades of mountain birch forests, along forest roads and other sun exposed areas in woodland or over mires. It perches mostly in trees or shrubberies and is rarely seen directly on the ground. Most commonly you only find single individuals but larger numbers of individuals can be seen when foraging or when they just have left the water. Males patrol slowly and low, flying back and forth within a rather restricted territories. It can make aggressive outbursts against other species if they enter the territory. Larvae live in shallow water or within wet Sphagnum moss. Exuviae are left high up on straws out in the water or along the shores.
Conservation Status
Similar Species
Somatochlora arctica, Somatochlora sahlbergi
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.