Emerald dragonflies

Emerald dragonflies
Spotted emerald dragonfly ( Somatochlora flavomaculata )
Systematics
Order : Dragonflies (Odonata) Subordination : Dragonflies (Anisoptera) Superfamily : Libelluloidea Family : Hawk dragonflies (Corduliidae) Subfamily : Corduliinae Genre : Emerald dragonflies
Scientific name
Somatochlora
Selys , 1871

The emerald dragonflies ( Somatochlora ) are a genus of the falcon dragonflies (Corduliidae) with currently 43 species described. They are mainly found around the Arctic in North America, Europe and Asia from southern India to the northern tropic ( circumboreal ). Individual species belong to the dragonflies with the northernmost and therefore coldest distribution areas and are adapted to cold regions due to their way of life, development times and physiological properties such as antifreeze in the larvae.

With 17 species, Canada is the state with the largest number of species and in North America it is the most species-rich genus of falcon dragonfly. Seven species can be found in Europe, three of which also live in Russian East Asia, where four other species exist. Seven species have been recorded for Japan , of which only S. clavata is endemic there , while the other species are also widespread in eastern Asia.

The emerald dragonflies got their German name because of their emerald green eyes, and the English name “Emeralds” or “Emerald dragonflies” for these dragonflies is derived from this.

features

The emerald dragonflies, both as larvae and as fully grown animals ( imago ), show only a comparatively low variance in their characteristics, especially with regard to body size and color.

Characteristics of the adults

Alpine emerald dragonfly ( Somatochlora alpestris ), frontal view of the head

Wings of the spotted emerald dragonfly ( Somatochlora flavomaculata )

The adults, which are medium in size with 39 to 68 millimeters, usually have a dark colored body with a metallic sheen and an indistinct light mark. Apart from some parts of the body, some of which are densely haired, such as the sides of the thorax , they are moderately hairy. A conspicuous sexual dimorphism does not exist in the species, gender differences are limited to the formation of the genital appendages on the abdomen and the shape of the abdomen, which is cylindrical in the females due to the ovaries located inside and filled with eggs, different from the males and in the third Abdominal segment has no constriction. This difference is particularly pronounced among the European species in S. metallica .

After the imago has hatched, the eyes are reddish brown and turn into a bright emerald green. The face is black with a metallic sheen, the metallic blue front usually has yellow side spots or a continuous yellow band and the labium is usually light. The thorax is metallic green and can produce copper-colored reflections. It is largely undrawn, but in some species it can have a maximum of one or two light spots or stripes. The abdomen is very dark - from black to metallic dark green - and has a species-specific, indistinct pattern of light spots and whitish intersegmental rings . The second abdominal segment is thickened.

The legs are usually black to blackish gray, with the front and rear legs of the males being equipped with a keel on the tibia , which the middle legs almost always lack. The wings are usually colorless, but can also be smoky gray or yellowish, especially at the front edge, especially in newly hatched females. The wing base is partly amber-colored. The wing veining is similar to the closely related falcon dragonflies ( Cordulia ), but differs from them by two additional transverse veins between the cubital vein and the anal vein . The wing triangles are two -lined , the sub- triangles of the fore wing three-lined and that of the hind wing one-lined and transparent. There is a single vein under the pterostigma . The hamuli , interlocking structures on the genitals of the males for mating, are large and flattened. They form hooks with the tip pointing backwards and the shape is species-specific.

The cerci (appendices superiores) are pointed and have ventral teeth, the shape is different depending on the species. The epiproct (appendix inferior) is shorter and elongated triangular, with the end often pointed and bent and more rarely blunted or slightly indented. The subgenital plate can vary greatly in shape and size, depending on the species; there are flat, trough-shaped and beak-shaped forms. With these variations of the abdomen, emerald dragonflies can best be distinguished and determined by the design of the abdomen appendages.

Characteristics of the larvae

The larvae correspond in their habitus to the typical falcon dragonfly larvae. They have a broad head (twice as wide as long) and the abdomen is more or less oval. The coloration is usually a single dark brown color, sometimes with black spots on the body and legs, but there are never dark stripes on the sides of the thorax. They are moderately to very hairy and have short to medium-long legs.

As is typical for falcon dragonflies, the trap mask is designed as a “helmet mask”, so it is not flat like the “plate mask” of other dragonfly larvae, but rather in the shape of a bowl. This deep shell is formed by the labial palps and the front part of the reshaped prementum and closed at the top by long, erect bristles. The inner edge of the labial palps is notched and has a pointed spike as a movable hook. The protective mask joint (labial suture) extends to the base of the mesothorax or to the attachment of the hips ( coxae ) of the middle pair of legs. The hind wing sheath extends in the larvae of the terminal stage (F-0) to the middle of the sixth abdominal segment.

Back spikes may be present on segments 3 to 9. Side spikes are formed at most on segments 8 and 9, but they can also be missing. The anal pyramid is about as long as the last two segments (9 and 10) together. In Europe, the larvae of the alpestris group ( S. alpestris , S. arctica , S. sahlbergi ) are differentiated from those of the metallica group ( S. metallica , S. meridionalis , S. flavomaculata , S. graeseri ). In the larvae of the first group, the hair is strong, back thorns are absent and side thorns are minimally developed, the latter have weak hair and are equipped with clear thorns on the back and sides.

Genetic traits

As with most insect groups, very little data on the genetics and genome of emerald dragonflies is available. So far, the genome of no dragonfly species has been completely sequenced . Individual gene segments of the nuclear DNA and the mitochondrial DNA of different species were used for comparative phylogenetic analyzes, e.g. for S. flavomaculata on the basis of 18S and 28S rRNA and for the species S. viridiaenea (in two subspecies) and S. clavata in Japan based on mitochondrial DNA.

In 2009, Ardila-Garcia and Gregory determined the size of the genome of S. williamsoni and S. elongata as part of an estimate of the genome size of around 100 dragonfly species . It was for S. William soni a genome mass of 1.9 pg (picograms), and for S. elongata of 2.85 pg determined (1 pg corresponds to approximately 1 billion base pairs ), the assessment as compared with known data for Drosophila melanogaster and Tenebrio molitor was . Within the study, S. elongata had the largest genome of all the species examined.

distribution

Even if many species can be found in more southern areas and S. dido in Taiwan and S. daviesi in southern India up to the northern tropic , emerald dragonflies are mainly holarctic in North America and Eurasia and mainly circumboreal . Individual species thus belong to the dragonflies with the northernmost and thus coldest distribution areas. Canada has the greatest abundance of species with 17 species . Seven species can be found in Europe, three of which also live in Russian East Asia , where four other species exist. Seven species have also been described in Japan , of which only S. clavata is endemic , while all others are also common in Eastern Asia.

The habitats of the emerald dragonflies vary depending on the species and region, with a preference for moorland areas . 14 of the 17 Canadian species are found in raised bogs and the European species are also predominantly represented in bog areas.

Way of life

Like all dragonflies, emerald dragonflies are dependent on water because of the aquatic development of their larvae. Adults sometimes move very far away from the breeding waters and some species even prefer to mate on hills. Only a few statements can be made that apply to all types of emerald dragonflies.

Lifestyle of the larvae

The larvae initially feed on the rest of their yolk supply , but start catching prey as early as the first week using their fully functional and fully trained capture mask . They eat opportunistically, so they catch almost anything that can overwhelm them. Emerald dragonfly larvae are stalking hunters on the ground and are mainly based on tactile stimuli, while the eyes only play a subordinate role in catching prey. As observed with S. metallica, they do not climb into the aquatic plants to catch prey, as occurs with other dragonfly larvae. Faecal analyzes of the larvae of S. alpestris in small alpine pools showed that the main food was mosquito larvae , water fleas , mud fly larvae , small mussels, annelid worms and water mites , but also tufted mosquito larvae , which are usually open water inhabitants, and larvae of their own species ( cannibalism ). When analyzing the stomach contents of S. arctica in Norway, 58 percent of the diet consisted of mosquito larvae and 40 percent of water fleas, the remaining 2 percent were water mites.

The larval waters of most emerald dragonflies are characterized by very low pH values ​​and high nutrient content (moor waters). The larvae are very tolerant of contamination and can live in waters of various properties from completely oligotrophic to strongly eutrophic , as well as in very soft to hard and strongly acidic to slightly alkaline water. Investigated larvae of S. alpestris and S. arctica did not damage the investigated larvae of S. alpestris and S. arctica for several weeks in water with a pH value of 3 or in distilled water . However, they are very sensitive to excessively high water temperatures, with constant temperatures of more than about 26 ° C being very unfavorable for the animals.

When compared to other dragonfly larvae, emerald dragonfly larvae are also considered to be very tolerant of freezing. They survive longer periods of frost at temperatures down to around –20 ° C without damage as long as the inside of the cell does not freeze. They do this by using special substances in the body fluids that act as anti-freeze ; polyhydroxy alcohols in particular fulfill this function. Another special adaptation of the emerald dragonfly larvae is their very long survivability when their larval waters dry out, which often happens in smaller pools, especially in high and late summer. Some of the larvae survive the dry periods in the dried-up mud; the larvae of the American S. hineana are said to retreat to crab burrows for this purpose. In a moist substrate such as leaf litter and moss cushions, the survival time is sometimes several months. In experiments, larvae of S. semicircularis were able to survive in the dry at 20 ° C and about 70 percent humidity on average for 13 days, while larvae of other species from the same waters dried out in half the time.

Lifestyle of the adults

Adult male of the shiny emerald dragonfly ( Somatochlora metallica ) on patrol flight

With the maiden flight the pre-productive phase of the imaginal life begins, during which the maturation of the adult dragonflies takes place. The maiden flight usually leads steeply into the treetops of the surrounding vegetation and, if there is no vegetation, can reach a few hundred meters. The susceptibility to predators - especially birds - is particularly high during this maiden flight, as the dragonflies, which are not yet fully cured, can only fly and maneuver relatively awkwardly. During the maturation period the dragonflies live in their maturation habitat in the vegetation area away from the water, for example in forest clearings and in loosely bushy terrain. The habitats of all emerald dragonflies have a similar structure. S. sahlbergi can be found in the sub-arctic birch forest and S. arctica in loosened coniferous forest, and they use the high tree areas as resting places.

Unlike many other dragonflies, emerald dragonflies (and also other falcon dragonflies) do not use waiting areas from which they spy and then hunt their prey, but hunt in flight. They hunt primarily small insects such as mosquitoes (mainly midges ) and fly . They fly through more or less straight to undulating, sometimes also in zigzag flights, especially the mating swarms of their prey and catch individual insects, which they grab with their mouthparts and chew in the air. They also hunt larger individual insects such as stone flies , mayflies or rainflies less often . The hunting of the four-spot dragonfly ( Libellula quadrimaculata ) has also been proven for S. metallica . The hunt usually takes place on land at some distance from the water in open places in the moor or on tree-poor slopes and open forest areas, while the dragonflies rarely catch insects in the mating place or water. Occasionally, emerald dragonflies hunt in a group, with the Japanese S. viridiaenea in a group of 23 individuals and the North American S. hineana even with 30 to 70 individuals. In contrast to this, S. alpestris can also form hunting grounds which it defends against conspecifics.

Reproduction and development

Reproduction

After the end of the ripening period and thus during the reproductively active period, both males and females stay in the area of ​​the breeding waters to mate , whereby the flight times vary depending on the species. According to investigations, S. flavomaculata is found in the mating water between 8:30 a.m. and 5:00 p.m., while S. alpestris can be found there until about 7:00 p.m. The North American S. linearis , on the other hand, can only be found in the mating waters in the early morning up to a maximum of 8:00 a.m.

The meeting point of the sexes (rendezvous place) corresponds to the egg-laying waters for most species. However, especially in species that lay their eggs in small bodies of water, such as S. arctica and S. alpestris , it can also lie away from the water. The males visit the rendezvous places in search of females ready to mate and sometimes patrol here for several hours or search the surrounding vegetation. Individual species are territorial and defend their territories against other males or other species. In Japan, for example, S. clavata forms territories on irrigation ditches in rice-growing areas. Territorial defenses were also observed in S. metallica on small lakes and in S. meridionalis on narrow rivers. Females, on the other hand, only rarely and then usually only for a short time at the rendezvous places, so that the proportion of males present is usually well over 90 percent (operational sex ratio (OSR)> 0.9), while the ratio in the overall population is more likely is balanced.

The mating of emerald dragonflies (and also other falcon dragonflies) is only very rarely initiated away from the rendezvous areas and the egg-laying waters. The females are recognized optically, the males only reacting to the type of movement and then recognizing the females by the shape of the abdomen. Mismatches are very rare, but individual species can hybridize with each other and produce viable common offspring. This is mainly documented by S. sahlbergi with S. hudsonica and S. albicincta in Yukon , Canada . The unmated females signal their willingness to mate through a special flight behavior in which they pause several times (pre-copulation flight, "premating flight"). If they are discovered in the process, a male will fly them to them and pack them for mating.

Mating wheel of emerald dragonflies (i. W. S .; here it is falcon dragonflies , Cordulia aenea ). The male holds the female behind the head, while the latter is coupled to the tip of the abdomen on the copulatory organ of the male below the second abdomen segment

Mating takes place in the same way for all falcon dragonflies and most of the large dragonflies. The male usually grabs the female with his legs from the top of the thorax and then “wanders” forward to the head. There it grabs the head of the female with the cerci and flies on with the female in tandem flight. By pulling the end of its abdomen forward again, it transfers sperm into the copulatory apparatus on the underside of the second abdominal segment. Then it asks the female to form the mating wheel , in which the female brings the end of her own abdomen under the male's copulatory apparatus and couples it there. While most species now quickly fly into the vegetation, some emerald dragonflies such as S. arctica and S. flavomaculata remain circling over the rendezvous place for several minutes and only then sit in a safe place in the vegetation where mating actually takes place.

The duration of copulation can also vary greatly within the species, it is usually between 15 minutes and almost an hour (or even more). The paired hamuli of the male are hooked to the subgenital plate of the female, while the "penis" is pushed between the two lobes of the subgenital plate and presses the sperm into the female genital opening with pumping movements. After copulation, the genitals first separate and only one or two seconds later the tandem grip is released before one of the partners flies off, while the other usually remains at the mating site for a short time.

Egg laying

The eggs are only laid some time after mating, with the female appearing alone at the egg-laying site and trying to avoid the males in order to be able to lay the eggs undisturbed and avoid further copulations. The females of S. flavomaculata , S. arctica and S. alpestris behave very inconspicuously within the vegetation. If they are discovered, they flee from the males towards the bank or signal unwillingness to mate with a downward-curved abdomen.

The fertilized eggs with the embryo they contain , which is formed in the egg from the zygote , are released into the water when the eggs are laid, whereby they are deposited in small groups with the emerald dragonflies and the closely related falcon dragonflies of the genus Cordulia . They emerge quickly one after the other from the genital opening and collect without sticking under the channel-shaped subgenital plate . As with all falcon dragonflies, the eggs emerging from the genital opening are dabbed on the surface of the water in small portions of 2 to 15 eggs in flight and then sink to the bottom of the water. They separate, then they sink and remain on the substrate of the water bed or on parts of plants. When water is absorbed in the exochorion , the eggs swell to a gelatinous state and stick to the substrate surface. In the case of the eggs of S. arctica and S. alpestris, it takes about 30 to 60 minutes for the eggs to become sticky and to settle after they sink. In the case of flowing water species, this process could go faster in order to prevent drift - however, corresponding studies are not available for emerald dragonflies. The number of eggs released is around 300 to 1,000 per female, although individual females can lay eggs several times.

However, in contrast to almost all other dragonflies, various emerald dragonflies also lay eggs on land. S. metallica, for example, lays packets of eggs in the soft substrate on the lakeshore by using the ovipositor to sink them about a millimeter into the ground. Something similar was also observed in S. meridionalis , S. sahlbergi , S. uchidai , S. williamsonis , S. elongata and S. minor ; the same behavior is assumed for other species with a similarly shaped ovipositor. In this way, the eggs escape aquatic predators, but the larvae must either actively enter the water after hatching or be washed in.

Embryonic development

As with all other dragonfly species, the development of the emerald dragonflies takes place after the eggs have been fertilized in the spermatheque (paired, tubular chambers in which the sperm of the males are stored after copulation ) in the eggs in the abdomen of the body of the female dragonflies. Sex development depends on whether the cells contain one or two X chromosomes after fertilization.

The embryo develops into a prolarva , which hatches in the water and develops into a complete larva here. The overall development from fertilization to hatching of the prolarve from the egg takes 19 to 21 days in S. viridiaenea . On the fourth day of development, the embryo's germinal strip has grown to about the length of the egg and on the following day the segments with the body appendages are formed. The embryo begins to roll out on the ninth day and fully matures in the remaining 10 days. The eye systems in emerald dragonflies consist of only seven individual eyes ( ommatidia ), in the genus Epitheca there are ten and in the noble dragonflies (Aeshnidae) even up to 270.

A very narrow temperature window with a range of around 10 ° C is necessary for embryonic development. S. arctica and S. alpestris probably cease to develop below 16 ° C; at permanent temperatures above 26 ° C, the eggs and embryos die.

Hatching takes place after the embryonic development is complete, however, between the completion of morphogenesis in autumn, the larvae overwintering in the egg have a diapause , so that they hatch in the following spring, induced by an increase in temperature. These diapause eggs have been found for S. arctica and S. alpestris , for example . When hatching, the prolarve saws open the egg membrane from the inside with a finely toothed comb on the head (analogous to the egg tooth of birds) and frees itself from the egg and jelly through winding movements. Hatching can take place during the day as well as at night, but focuses on the time immediately after sunset and is likely induced by the change in light.

Larval development

The larval development of the emerald dragonflies, like other dragonflies, represents the longest phase of life and - depending on the species - usually takes several years. The development time of S. arctica and S. alpestris is estimated to be at least three years each with two to three hibernations. For species with distribution areas very far north, such as S. semicircularis in Colorado and S. sahlbergi in Yukon , Canada, the development time is even four to five years.

The prolarva stage (already called the first larval stage by some authors) is about one millimeter long and translucent after hatching. Further development takes place over at least 11 moults , which means that 12 to 14 larval stages are possible. The body size increases by about a quarter with each moult, the duration of the stages also increases and in some species can decrease again in later stages. In some species, a so-called crowding effect occurs when several larvae of the same clutch grow up in the same small body of water and thus compete for food. In this case it has been demonstrated for hand-rearing S. arctica that only one individual develops normally, while the others remain behind in growth even with optimal nutrition. This is particularly important when the larvae grow up together in very small ponds, as is the case with some emerald dragonflies.

Before the transformation to the imago, most larvae have another diapause to overwinter in the last larval stage, which means that the completion of larval development can be synchronized and the adults hatch and fly out almost simultaneously in early spring.

Conversion to Imago

In juvenile adults - here a recently hatched male of the shiny emerald dragonfly ( Somatochlora metallica ) - the complex eyes are initially not yet green

The completion of the larval development is the imaginal molting (hatching) and the change in the habitat and the way of life from aquatic life to land life (excursion or emergence). The transformation of the larva to the imago, the metamorphosis , is hormonally controlled in all insects by the ecdysone and the juvenile hormone and takes place at the end of the last larval stage through a sudden increase in ecdysone and a lack of the juvenile hormone. In dragonflies, the formation of the imaginal organs, especially the sexual organs, is completed, and larval features such as the trap mask are receded a few days before the last moult.

Shortly before the transformation to the imago, the larva emerges from the larval water on a stalk or other substrate and clings to it above the water surface. This is preferably done in the area of ​​the bank. Breathing occurs through already formed trachea with breathing openings (stigmata) on the thorax. In this position, the larval skin dries and is detached from the new skin by the dragonfly through what is known as "pumping". During this time the legs are “circled” for better anchoring, which is typical for falcon dragonflies and has been described for S. meridionalis , among other things . The skin bursts in the area of ​​the wing sheaths and the crack expands over the wing systems and the head. The head and thorax protrude from this opening, after which the legs, wings and abdomen are freed from the larval skin. After the imago has completely emerged from the larval envelope, the wings, which were strongly unfolded in the wing sheaths before hatching, unfold by pumping in hemolymph . At the same time, the abdomen is stretched and the dragonfly is completely hardened and colored. Imaginal life begins with the subsequent maiden flight .

The emergence of the emerald dragonflies occurs either at the beginning of the warm season in spring (spring species), with the last larval moult taking place before winter, or after one or two more moults in early summer (summer species). Thus S. alpestris as Frühjahrsart and S. metallica described as summer while S. arctica regionally both spring may be summer like. Hatching takes several hours, a duration of about 3.5 hours for S. alpestris and 4.5 hours for S. arctica was observed. In most species it takes place in the morning. For S. semicircularis from the Rocky Mountains it could be proven that by noon around 75 percent of the daily cohort hatched and the remaining dragonflies took off in the hours immediately following.

Imaginal life

The imaginal life, i.e. life as a fully-grown and ultimately reproductive dragonfly, is only very short compared to the larval development of several years. An average lifespan of 50 days is assumed for falcon dragonflies; field tests with S. alpestris have shown a maximum of 66 days and an average of only 45 days.

However, the dragonflies are not yet able to reproduce after emergence, but still require a short maturation period, which they spend in the surrounding vegetation. During this time, the animals harden completely, whereby the initially brown eyes change color to a bright emerald green, the dark body receives the typical green metallic sheen and the sexual organs develop completely. The maturation period for the emerald dragonflies is between 7 and 28 days, for S. uchidai even up to 36 days for the male and 32 days for the female with a maximum established lifespan of 69 days for the males and 49 days for the females.

Predators and parasites

Enemies of the larvae and avoidance of feeding

Both the larvae and the adults are often prey of other predators ( predators ). The larvae are mainly captured by dragonfly larvae (some of their own species) and by fish, although no genus-specific differences between emerald dragonflies and other dragonfly larvae are documented in this regard. For the closely related Epitheca cynosura , it was determined that up to 60 percent of the young larvae are decimated by other dragonfly larvae and fish within one month of hatching in the first larval year; for Cordulia amurensis , calculations are even available that after the five-year development period only about 0 , 2 percent of the original larvae survive to hatch.

The various possibilities of camouflage and hiding, as well as laying eggs in very small and mostly acidic waters that do not contain any fish, serve to protect against predators . The latter is practiced by S. arctica and S. alpestris , which lay their eggs in very small bodies of water in the bog, where there is no feeding pressure from fish. Other species such as S. meridionalis are strongly flattened and have a body-dissolving (somatolytic) color pattern on the abdomen, which means they are very well camouflaged on the ground. S. alpestris , on the other hand, has a highly arched abdomen with a dense set of bristles in which peat particles are caught so that the larvae are camouflaged in the peat mud. If the larvae are discovered and attacked in spite of camouflage, a dead reflex (thanatose) ensues. Like many other dragonfly larvae, S. metallica , S. meridionalis and S. flavomaculata also have strong thorns on the back and sides of the abdomen, through which the larger larvae together with their splayed legs keep fish from eating. Experiments have shown that some dragonfly larvae develop larger thorns in the presence of fish and have larger thorns in fish-rich waters. However, no studies are available for emerald dragonflies.

Parasite infestation is only poorly documented in emerald dragonfly larvae. In general, dragonfly larvae are infested by gregarines and larval stages by tapeworms , suction worms and string worms . In fact, of S. metallica a tapeworm of the genus an infestation of larvae Schistotaenia be detected in the same way also the strings worm was Gordius aquaticus . In addition to these parasitic colonizers dragonfly larvae also can be used as substrate for sessile protozoa and small animals such as vorticella (for example spec Zoothamnium. ), Hydra ( Hydra sp. ) And bryozoans (e.g. Fredericella ) are used, inter alia, at p metallica were detected ( Epizoose ).

Predators of the adults

The bee eater is one of the most effective dragonfly hunters in the region; locally up to 20 percent of the nestling food is S. flavomaculata

Because of their color and speed, the adults of the falcon dragonflies are comparatively seldom prey to predators. They are particularly susceptible during imaginal moulting and maiden flight, as a mating wheel and when laying eggs. Occasional capture has been demonstrated for a number of bird species, including the chaffinch , barn swallow and swallowtail . The genus can be more important as food for the bee-eater , with the latter observed in southeastern Poland that locally up to 20 percent of the nestling food consisted of S. flavomaculata . There are also frogs , predatory flies and other large dragonflies that can hunt emerald dragonflies, and more rarely also spiders and fish.

Dead and dying dragonflies that fall weakened on the surface of the reproductive waters are attacked and sucked out by water striders, and dragonflies caught in spider webs can be eaten by scorpion flies and other scavengers.

The parasites of the adults include above all the gregarines, which already attack the larvae, as well as suckers and tapeworms, which the dragonflies use as intermediate hosts and, as final hosts, usually attack insect-eating birds. In addition, the larvae of the water mite genus Arrenurus , in Europe exclusively Arrenurus pustulator, are ectoparasites . These look for dragonfly larvae that are ready to hatch and, during the imaginal molt, they move over to the dragonflies, where they feed on the dragonfly's hemolymph through a suction tube ( stylosome ) on the underside of the rear abdominal segments and fall back into the water after the parasitic development phase, which lasts three to four weeks to let. The infestation can range from very few mites to over 1,000 mites on a dragonfly. So far only S. metallica and Cordulia aenea have been identified as hosts for the mites in Europe .

Ectoparasites also include midges of the genus Forcipomyia , which, in addition to other dragonflies, also attack S. arctica , S. uchidai and S. flavomaculata and attach themselves to the wing veins near the wing base with their stinging-sucking mouthparts, where they suck the hemolymph. As a rule, there are a maximum of two to three midges on a dragonfly.

Evolution and systematics

Fossil record

The fossil record of corduliidae whole is very sparse, and the assignment is difficult, as the systematic discussions have shown. Molecordulia karinae from the Paleocene of Denmark, which was described in 2005 and is around 65 million years old , is the oldest fossil find that was definitely assigned to the falcon dragonflies .

The oldest find of an emerald dragonfly is possibly from the Miocene of Bulgaria (5 to 24 million years ago), but the current assignment as Somatochlora alpestris is also controversial.

External system

→ Main article : Falcon dragonflies

The emerald dragonflies are classified as a genus within the falcon dragonflies (Corduliidae) and thus in the Libelluloidea . A total of 39 genera are currently distinguished within this family, although the monophyly of the falcon dragonflies in relation to the sail dragonflies (Libellulidae) has been questioned by several authors. This applies in particular to the genus Macromia and some associated genera, which have accordingly been separated out by some authors as a separate family Macromiidae, as well as the genus group around the river hawk ( Oxygastra ) and a number of other genera, which are regarded as sister groups to all of the remaining dragonflies and the sail dragonflies .

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Relationships between falcon and sail dragonflies according to Ware et al 2007:

Libelluloidea	GSI group ( corduliidae ., U. A Oxygastra , Macromidia , Gomphomacromia )   MCL group    Corduliinae (falcon dragonflies, including Somatochlora , Cordulia , Epitheca )      Macromiidae (falcon dragonflies , including Macromia , Didymops , Phyllomacromia )      Libellulidae (dragonflies)

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Within the falcon dragonflies, the emerald dragonflies are grouped together with some genera (including Cordulia and Epitheca ) to form the Corduliinae (or Corduliidae sensu stricto), which are considered monophyletic. No information is available on the monophyly of the genus itself, but it is also not in doubt. The sister group is not clearly identified.

Internal system

Alpine emerald dragonfly ( Somatochlora alpestris )

The first description of the genus as somatochlora , which is valid today, was made by Edmond de Selys-Longchamps in 1871. The scientific name is derived from the Greek names sôma for “body” and chlôros for “green”, meaning “green body”. The older name Chlorosoma , which was given to the genus by Toussaint von Charpentier in 1840 and was composed of the same words in a different order, had the same meaning . However, since this name had already been assigned to the genus of adder known today under the name Philodryas , it became invalid and replaced by the name given by Edmond de Selys-Longchamps.

Within the emerald dragonflies, depending on the author, about 40 species are differentiated, with the differences in the number of species being primarily due to the potential synonymisation of individual species as subspecies of others. The following list of species is based on Schorr et al. 2014 and lists 43 species:

• Somatochlora albicincta ( Burmeister , 1839)
• Alpine emerald dragonfly ( Somatochlora alpestris ( Selys , 1840))
• Arctic emerald dragonfly ( Somatochlora arctica ( Zetterstedt , 1840))
• Somatochlora brevicincta Robert , 1954
• Somatochlora calverti Williamson & Gloyd , 1933
• Somatochlora cingulata ( Selys , 1871)
• Somatochlora clavata Oguma , 1922
• Somatochlora daviesi Lieftinck , 1977
• Somatochlora dido Needham , 1930
• Somatochlora elongata ( Scudder , 1866)
• Somatochlora ensigera Martin , 1907
• Somatochlora exuberata Bartenev , 1910
• Somatochlora filosa ( Hagen , 1861)
• Spotted emerald dragonfly ( Somatochlora flavomaculata ( Vander Linden , 1825))
• Somatochlora forcipata ( Scudder , 1866)
• Somatochlora franklini ( Selys , 1878)
• Somatochlora georgiana ( Walker , 1925)
• Somatochlora graeseri ( Selys , 1887)
• Somatochlora hineana Williamson , 1931
• Somatochlora hudsonica ( Hagen , 1871) in Selys
• Somatochlora incurvata Walker , 1918
• Somatochlora kennedyi Walker , 1918
• Somatochlora linearis Hagen , 1861
• Somatochlora lingyinensis Zhou & Wa , 1979
• Somatochlora margarita Donnelly , 1962
• Balkan emerald dragonfly ( Somatochlora meridionalis Nielsen , 1935)
• Shiny emerald dragonfly ( Somatochlora metallica ( Vander Linden , 1825))
• Somatochlora minor Calvert , 1898
• Somatochlora nepalensis Asahina , 1982
• Somatochlora ozarkensis Bird , 1933
• Somatochlora provocans Calvert , 1903
• Polar emerald dragonfly ( Somatochlora sahlbergi Trybom , 1889)
• Somatochlora semicircularis ( Selys , 1871)
• Somatochlora septentrionalis ( Hagen , 1861)
• Somatochlora shanxiensis ( Zhu & Zhang , 1999)
• Somatochlora taiwana Inoue & Yokota , 2001
• Somatochlora tenebrosa ( Say , 1840)
• Somatochlora uchidai Forester , 1909
• Somatochlora viridiaenea ( Uhler , 1858)
• Somatochlora walshii ( Scudder , 1866)
• Somatochlora whitehousei Walker , 1925
• Somatochlora williamsoni Walker , 1907

Hazard and protection

Within the emerald dragonflies there are some species that are considered endangered regionally or in their overall distribution. The International Union for Conservation of Nature and Natural Resources (IUCN) has 13 somatochlora species on the Red List of Threatened Species , of which only two are assessed as endangered ("vulnerable") and three as species on the warning list ("near threatened") while the other species are regarded as not at risk (“least concern”) or the data situation is insufficient for a risk assessment (“data deficient”).

The endangered species S. margarita is characterized by a very small distribution area - S. margarita is endemic in two US states. The three species on the warning list ( S. hineana , S. ozarkensis and S. calverti ) also have a very limited range and were therefore classified accordingly.

supporting documents

1. ↑ James George Needham, Minter Jackson Westfall, Michael L. May: Dragonflies of North America. ISBN 0-945417-94-2 .
2. ↑ ^{a b c d e f g h i} Genus Somatochlora SELYS. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 373-374.
3. ↑ ^{a b} Development in the ovary: from the oogonium to the egg. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 46-47.
4. ↑ ^{a b c d} Development environment water - liquid, ice-shaped or evaporated. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 78-82.
5. ↑ Rasmus Hovmöller, Thomas Pape, Mari Källersjö: The Palaeoptera Problem: Basal Pterygote Phylogeny Inferred from 18S and 28S rDNA Sequences. Cladistics 18, 2002; P. 313–323 ( PDF ( Memento of the original from December 22, 2009 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. ). 
6. ↑ Yuzo Takegawa, Hideo Fukuda, Kenta Totsuka, Hisashi Kimoto, Akira Taketo: Phylogenetic Relationship among Several Japanese Odonate Species Inderred from Mitochondrial DNA Sequences. Memoirs of the Fukui Institute of Technology 37, 2007; Pp. 235–242 ( PDF ( Memento of the original from April 30, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. ). 
7. ↑ AM Ardila-Garcia, T. Ryan Gregory: An exploration of genome size diversity in dragonflies and damselflies (Insecta: Odonata). Journal of Zoology 278, 2009; Pp. 163-173 ( PDF ).
8. ↑ Find food and catch prey. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 86-99.
9. ↑ ^{a b} Maturation away from the water. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 140-145.
10. ↑ ^{a b c} Hunters and the hunted. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 150-157.
11. ↑ Seasonal flight periods and daily activity patterns. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 145-149.
12. ↑ ^{a b} Meeting place of the sexes - the rendezvous place. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 213-219.
13. ↑ Are falcon dragonflies territorial? In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 220-231.
14. ↑ ^{a b c} Pairing initiation after lightning attack. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 231-239.
15. ↑ Sydney G. Cannings, Robert A. Cannings: Dragonflies (Odonata) of the Yukon. In: HV Danks and JA Downes (Eds.): Insects of the Yukon. Biological Survey of Canada (Terrestrial Arthropods). Ottawa 1997; Pp. 169-200 ( PDF ).
16. ↑ During and after mating. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 239-245.
17. ↑ ^{a b} Egg-laying - if possible without disturbing males. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 250-259.
18. ↑ ^{a b c} single eggs, spawning balls and spawning lines. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 51-55.
19. ↑ ^{a b c} Klaus Sternberg: Influence of oviposition date and temperature upon embryonic development in Somatochlora alpestris and S. arctica (Odonata: Corduliidae). Journal of Zoology 235 (1), 1995; Pp. 163-174. doi : 10.1111 / j.1469-7998.1995.tb05135.x .
20. ↑ Kozo Miyakawa: Rotation of Embryo in Eggs of Petaluridae, Gomphidae, and Corduliidae, in Connection with Types of Oviposition, Egg Shape and Germ Band (Odonata, Anisoptera). Japanese journal of entomology 58 (3), 1990; Pp. 447-463 ( full text ).
21. ↑ ^{a b} From the zygote to the prolarve. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 59-65.
22. ↑ ^{a b c} Long preparation for a short adult life. and growth - development in unequal steps. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 70-78.
23. ↑ ^{a b c} From water to land life: metamorphosis and emergence. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 111-135.
24. ↑ ^{a b c} Imaginal stage - last stage of individual life. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 136-140.
25. ↑ ^{a b} Avoid Enemies - Subject with variations. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 99-108.
26. ↑ Freeloaders and free riders. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 108-110.
27. ↑ ^{a b} Endo- and ectoparasites. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 157-162.
28. ↑ ^{a b} The Libelluloidea - a young family group. In: Hansruedie Wildermuth: The falcon dragonflies in Europe. Pp. 27-29.
29. ^ Martin Schorr, Martin Lindeboom, Dennis Paulson: World Odonata List. Update from February 10, 2010 ( download ).
30. ↑ ^{a b c} Jessica Ware, Michael May, Karl Kjer: Phylogeny of the higher Libelluloidea (Anisoptera: Odonata): An exploration of the most speciose superfamily of dragonflies. Molecular Phylogenetics and Evolution 45 (1), 2007; Pp. 289-310.
31. ↑ first description as a synopsis of the Cordulines. Bulletin de l'Académie royale des Sciences de Belgique (2) 31, 1871: pp. 238-318.
32. ^ Martin Schorr, Martin Lindeboom, Dennis Paulson: World Odonata List. Update from December 1, 2014 ( download ).
33. ↑ Search result Somatochlora in the Red List of Threatened Species of the IUCN ..
34. ↑ Somatochlora margarita in the IUCN Red List of Threatened Species 2010.1. Listed by: Abbott, JC, 2006. Retrieved March 29, 2010.
35. ↑ Somatochlora hineana in the IUCN Red List of Threatened Species 2010.1. Posted by: Abbott, JC & Cashatt, E., 2007. Retrieved March 29, 2010.
36. ↑ Somatochlora ozarkensis in the IUCN Red List of Threatened Species 2010.1. Listed by: Abbott, JC, 2007. Retrieved March 29, 2010.
37. ↑ Somatochlora calverti in the IUCN Red List of Threatened Species 2010.1. Listed by: Paulson, DR, 2007. Retrieved March 29, 2010.

literature

• Hansruedie Wildermuth: Europe's falcon dragonflies. (= Die Neue Brehm-Bücherei. Volume 653). Westarp Sciences Hohenwarsleben 2008, ISBN 978-3-89432-896-2 .
• Garrison, von Ellenrieder , Louton: Dragonfly Genera of the New World. The Johns Hopkins University Press, Baltimore 2006, ISBN 0-8018-8446-2 , pp. 168 ff.
• James George Needham, Minter Jackson Westfall, Michael L. May: Dragonflies of North America. Smithsonian Institution Press, 2001, ISBN 0-945417-94-2 .
• Klaus Sternberg, Rainer Buchwald (ed.): The dragonflies of Baden-Württemberg. Volume 2: Dragonflies (Anisoptera). Verlag Eugen Ulmer, Stuttgart 2000, ISBN 3-8001-3514-0 , p. 236 ff (species portraits for S. alpestris , S. arctica , S. flavomaculata and S. metallica ).
• Edmund Murton Walker: The North American Dragonflies of the genus Somatochlora. University of Toronto, 1925.

Web links

Commons : Emerald Dragonflies ( Somatochlora )  - Album with pictures, videos and audio files

• Günter Bechly: Phylogenetic Systematics of Odonata. Retrieved February 18, 2011 . 

This article was added to the list of excellent articles on May 29, 2010 in this version .