Great darter
| Great darter | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
.jpg)
Great darter |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Sympetrum striolatum | ||||||||||||
| ( Charpentier , 1840) | ||||||||||||
| Subspecies | ||||||||||||
|
The great darter ( Sympetrum striolatum ) is a type of dragonfly from the family of the sail dragonflies (Libellulidae). These form a family of the suborder dragonflies (Anisoptera). The dragonfly is quite frugal when it comes to choosing the populated waters. It inhabits both shallow, warm ponds and pioneer waters such as sand pits. The main flight time in Central Europe is between July and October. The existence is considered to be secured.
The great darter owes its name to the fact that it is the largest representative of its species in Germany. The second part of the species name ( epithet ) striolatum (m. Striolatus , "with small stripes") refers to the pattern of the breast section. The species occurs in some subspecies with a distribution center in Asia .
distribution
The great darter is a widespread species. The nominate form occurs in northern Africa , in Europe excluding northern Scandinavia and in Asia Minor and West Asia . In Europe, the main area of distribution is in the Mediterranean area . In Mongolia and Buryatia the subspecies Sympetrum striolatum doshidordzii is represented, in Manchuria , North Korea , the easternmost parts of Russia and on the Kuril Islands, however, Sympetrum striolatum imitoides . The endemic subspecies Sympetrum striolatum kurile also occurs on the Kuril Islands . Sympetrum striolatum pallidum, however, is endemic to Turkestan .
features
Construction of the Imago
The abdomen of the male Great Darter measures 26 to 29 millimeters, making the species the largest darter in Germany. The females are insignificantly smaller and reach an abdomen length between 25 and 28 millimeters. Their wings are between 27 and 30 millimeters long and vary in width from 2.9 to 3 millimeters at the base. The males, on the other hand, measure 27 to 29 millimeters in length and are 2.9 to 3.2 millimeters wide.
Directly after the metamorphosis to the imago there are no sexual dimorphisms in the coloration. The females and males are pale green on the abdomen at this point. The chest section ( thorax ) is light pink in front, the sides are yellow and provided with delicate brown lines. The forehead shows a pale yellow ocher, the complex eyes are chocolate brown above, yellow-green below. It takes about two weeks for the final ocher yellow color to appear.
With aging, the animals color and color differences develop between the sexes. In the males, a red hue starts at the median line . Two bright side stripes appear on the thorax, which allow the species to be differentiated from other species. In the females, however, the thorax remains pale and red traces can only be seen on the abdomen in the immediate vicinity of the median line.
Furthermore, the head has a black forehead markings that end at the eyes, while in the common darter ( Sympetrum vulgatum ) it continues a little way down the eyes. The legs are black and have a red to yellow color on the top, which is not found in the similar blood-red darter ( Sympetrum sanguineum ).
Construction of the larva
The larvae of the great darter are sparse and sepia colored. They are around seven millimeters wide and 18 millimeters long. The pentagonal head, which is slightly convex on the top, makes up about 5.5 millimeters. The occiput extends far back and there are some bright spots on the vertex . On the front edge of the head are the almost hemispherical, large eyes. The pinpoint eyes ( ocelli ) are also clearly visible. The antennae consist of seven limbs, the first two of which are thickened and the remaining five are slender. The mentum narrows backwards towards the joint which is almost at the level of the middle pair of legs. The buttons (palps) are triangular and strongly concave . They are also studded with eleven bristles, although the number can vary somewhat. The Mentum, on the other hand, has 14 bristles.
In the last larval stage, the wing sheath on the thorax is five millimeters long. The length of the comparatively long legs increases from the front with about ten millimeters over the middle (about eleven millimeters) to about 16 millimeters backwards. On segments five to eight of the abdomen there are small thorns in the middle, the first of which is covered by the wing sheath. On the eighth and ninth segments there are also thorns on the sides. While those of the eighth segment are relatively short, these outgrowths on the ninth are roughly as long as the last two segments combined. The very hairy abdominal appendages are relatively short. While the dorsal ones are roughly the length of the ninth and tenth segments, the cerci are only about a quarter as long.
Similar species
Since many species of darter are very similar, it is sometimes difficult to distinguish them. The greatest danger of confusion is with the common darter ( Sympetrum vulgatum ). The two species are so similar, especially towards the end of the flight time, due to the darkness of the great darter, that the great darter was mistaken for not yet fully colored common darter in the last century. The two species can be differentiated from the fact that the black forehead line of the great darter ends at the eyes. The light side stripe on the chest can also provide information about the species, as it is much less pronounced in the common darter. For the males, the last third of the abdomen is also a distinguishing feature, as this is hardly widened in the great darter. In the females of the great darter, the laying tube protrudes diagonally from the abdomen, whereas in the females of S. vulgatum it is at right angles to the rear edge.
habitat
When choosing the populated waters, the dragonfly is quite frugal as long as they are around 16 ° C to 21 ° C.
Larval habitat
The larvae stay between plants growing under water at a not too great depth. Thousand leaf and water hose are preferred . If there are not too many fish in the water, they can also be found in ungrown areas of the water. In shallow water zones, the larvae also live on the bottom. Overall, regardless of whether they live in the submerged vegetation or on the ground, the animals seek out water zones that are not overgrown and that are well-lit by the sun. The populated bodies of water are stagnant bodies of water which are at most moved on the surface by the wind . The depth at which the larvae can be found depends primarily on the heat balance of the water. They can also be found at a depth of one meter when the water there is still between 16 ° C and 21 ° C. Usually, the larvae do not dive that deep. The animals make few demands on the acidity of the water. Eutrophic waters are preferred . Only very acidic moor waters with pH values below five do not colonize the larvae. The larvae do not survive drying out.
Imaginal habitat
After hatching, the great darter moves between 30 and 200 meters from the water, when the wings are sufficiently hardened, in order not to become easy prey for the birds that regularly search the water's edges. For the further ripening process, however, the animals of the species sometimes move several kilometers away from the slip waters. They mainly look for meadows, clearings, paths and gardens. For reproduction, the animals choose waters that meet the habitat requirements of the larvae. The bank should be flat and not overgrown. Like the larvae, the adults avoid shaded areas.
Way of life
Phenology
.JPG)
The flight time of the adults in Central Europe begins at the beginning of June at the earliest and lasts until the beginning of November. If the weather is good, the season can also extend into December. The maximum of hatching is reached in the second half of August. Compared with other dragonfly species, the flight time is extremely long. During the day, the dragonfly begins its flight as early as eight o'clock on warm summer days. However, reproductive activity does not usually start until 9 a.m. and ends around 2 p.m. At this time, the animals also withdraw to more protected areas of the water. On colder days in autumn, the daily routine shifts towards the warmest times.
To warm up the flight muscles, the great darter uses not only the orientation to the position of the sun but also the heat generated by the movement of the muscles . To do this, it trembles its wings, especially at temperatures below 13 ° C. This trick enables the species to start even at low temperatures around 10 ° C. Species that rely solely on the heat supply from the sun, such as the blood-red darter, can only fly up from around 14 ° C. An interesting temperature-dependent characteristic of the species is that the hue of the female abdomen turns dark red within 10 hours at temperatures below 12 ° C. If the temperature rises again, the abdomen will also turn lighter again within 30 to 40 minutes. Presumably, this color change serves to better regulate body temperature. The species usually feeds on small flying insects, such as mosquitoes or horseflies , but has no special requirements, but eats anything that can overwhelm it.
Similar to the Vierfleck , the great darter also forms swarms from time to time . However, these are usually much smaller. But the species also operates in a comparatively large area in everyday life. Action radii of around 1,300 meters have already been observed.
The species is sometimes attacked by mites of the genus Arrenurus . These sit at the base of the wings and suck in the hemolymph until they fall off by August at the latest.
Reproduction
Males ready for mating wait on a three to five meter high lookout and watch females flying by. The individual males usually do not come closer than ten to 15 meters. But they do not have a fixed territory. For mating, males and females form a tandem. To do this, the male reaches behind the head of the female with his abdominal appendages. Following this, the couple lands and the female moves the genital opening at the end of her abdomen to that of the male at the beginning of the abdomen. Finds of living males coupled with dead females and other observations indicate that it is not possible for the male to break away from the female on his own. This detachment usually occurs when the female clings to emersed vegetation while the male detaches by flying away. After separation, the female lays eggs for about 20 minutes, initially guarded by the male. It is deposited by dipping the tip of the abdomen into the water. After mating is complete, both partners can mate again. However, it probably takes a few days for the female to form fertile eggs again. The clutches contain up to several thousand eggs, with a single egg only about 0.3 millimeters wide and 0.6 millimeters long. Due to the less specialized copulation apparatus, darter species often mismatch with unrelated partners. This is compounded by overlapping habitats and the similarity of many species.
Embryonic development
The development of the embryos is largely not understood and shows some properties that are atypical for dragonflies. In laboratory tests, for example, the time it takes for the larva to hatch from the egg slows down significantly when the temperature is increased from 16 ° C to 21 ° C, and decreases again when the temperature is increased to 26 ° C. However, the duration at 26 ° C is still significantly longer than that at 16 ° C. With other dragonflies, on the other hand, the development time decreases steadily with increasing temperature. But even at the same temperature, the development time fluctuates enormously and is between ten and 60 days. The age of the female from whom the eggs came, as well as the photoperiod , the date of egg laying and the temperature mentioned above , obviously play a role. A diapause is rare in down before September eggs. This is attributed to the origin from Mediterranean areas. Towards the end of September and especially in October the number of eggs from which the larvae hatch only after hibernation increases. Those eggs typically take between 80 and 184 days to develop. Even if the great darter now lives almost exclusively in bodies of water that carry water continuously, the eggs can apparently survive dry periods unscathed. Here, too, one suspects the cause in adaptations to the original area of distribution in the Mediterranean area with its ephemeral waters.
Larval development
Under favorable conditions, the larvae develop within twelve to 15 weeks. Usually, the animals complete eight to ten molts during development. Approximately after the fourth molt, the animal measures three millimeters and the wing sheath becomes partially visible for the first time. Also with the fourth moult, the time intervals between two moults become uniform. While these previously fluctuated between 42 and 12 days, afterwards they are around 8 days. In warmer areas there can be two generations per season. Usually only one occurs in Germany . Further north, a two-year development period is also common. To hatch, the larvae climb stalks of sedge sticking out of the water . They can then be found ten to 30 centimeters above the water level.
Systematics
The great darter is classified in the genus darter ( Sympetrum ), which was created by Newman in 1833. Within the genus, the great darter is described as the closest relative of the common darter ( S. vulgatum ) and the black darter ( S. danae ). This is based on enzymatic studies.
There are five subspecies within the species. These are S. striolatum doshidordzii , S. striolatum imitoides , S. striolatum kurile , S. striolatum pallidum and S. striolatum striolatum . There are also two candidates for other subspecies. On the one hand, Sympetrum nigrifemur , which is probably a species, and Sympetrum nigrescens . Both can be found on islands, which would make it possible to explain their genesis through genetic drift .
Scientific descriptions
The German entomologist Toussaint von Charpentier first described the species in 1840. On the one hand, he had a male from Silesia , which he described as Libellula striolata . On the other hand, he was able to fall back on a copy from Portugal , but he did not specify the gender. In addition, he did not recognize the equality of the species and described the latter as Libellula ruficollis . The holotype is now in the French National Museum of Natural History ( Muséum national d'histoire naturelle ) in Paris . Another synonym created in the following year Sélys , who described an animal as Libellula macrocephala . In 1905 Jacobson and Bianki downgraded the species to a subspecies and added Sympetrum striolatum pallidum, which was first described in 1887, to the side. Ten years later, Bartenef added the Sympetrum striolatum imitoides , which he described for the first time in the same publication using a female from Vladivostok . The animal on which the description is based is now in the St. Petersburg Zoological Museum . The fourth subspecies, Sympetrum striolatum doshidordzii , was described in 1958 by Belyshev and Doshidordzii based on a male from Mongolia. In 1976 Belyshev presented another description of a male from the Kuril Islands as the fifth subspecies Sympetrum striolatum kurile .
literature
- Heiko Bellmann: Observe dragonflies - determine. Naturbuch Verlag, Augsburg 1993, ISBN 3-89440-107-9 .
- Paul-A. Robert: Die Libellen (Odonaten) - Authorized translation by Otto Paul Wenger. Kümmerly & Frey, Geographischer Verlag, Bern 1959.
- Jill Silsby: Dragonflies of the World. The Natural History Museum, Plymouth 2001, ISBN 0-565-09165-4 .
- Klaus Sternberg, Rainer Buchwald (ed.): The dragonflies of Baden-Württemberg. Vol. 2. Large dragonflies. Eugen Ulmer, Stuttgart 2000, ISBN 3-8001-3514-0 .
- William John Lucas: The Aquatic (Naiad) Stage of the British Dragonflies (Paraneuroptera). The Ray Society, London 1930.
Web links
- More photos at www.brocross.com
- Sympetrum striolatum inthe IUCN 2013 Red List of Threatened Species . Posted by: Clausnitzer, V., 2007. Retrieved February 18, 2014.
Individual evidence
- ↑ Holger Hunger among others: Distribution and phenology of dragonflies in Baden-Württemberg (Odonata). In: Libellula Supplement. 7 GdO, Börsen 2006, p. 177.
- ↑ a b c d e f g h i j k l m Klaus Sternberg, Rainer Buchwald: Die Libellen Baden-Württemberg. Volume 2: Dragonflies. Eugen Ulmer, Stuttgart 1999, 2000, ISBN 3-8001-3514-0 .
- ↑ a b Jill Silsby: Dragonflies of the World. The National History Museum, 2001, ISBN 0-565-09165-4 , p. 168.
- ^ A b Henrik Steinmann: World Catalog of Odonata. Part II: Anisoptera. de Gruyter, 1997, ISBN 3-11-014934-6 , p. 483.
- ↑ a b Paul-A. Robert: The dragonflies (odonates). Translation by Otto Paul Wenger. Kümmerly & Frey, Geographischer Verlag, Bern 1959, p. 284ff.
- ^ William John Lucas: The Aquatic (Naiad) Stage of the British Dragonflies (Paraneuroptera). The Ray Society , London 1930, pp. 79ff.
- ↑ Heiko Bellmann: Observe dragonflies - determine. Naturbuch Verlag Augsburg, 1993, ISBN 3-89440-107-9 , p. 232ff.
- ^ Matthias Zimmermann: Large darter. In: www.natur-lexikon.com. Retrieved June 24, 2007 .
- ↑ Paul-A. Robert: The dragonflies (odonates). Translation by Otto Paul Wenger. Kümmerly & Frey, Geographischer Verlag, Bern 1959, p. 381.
