Spotted darter
| Spotted darter | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
.jpg)
Spotted darter ( Sympetrum flaveolum ), male |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Sympetrum flaveolum | ||||||||||||
| ( Linnaeus , 1758) |
The spotted darter ( Sympetrum flaveolum ) is a species of dragonfly from the family of the sail dragonflies (Libellulidae). These are a family of the dragonflies (Anisoptera).
features
With a wingspan of five to six centimeters and a body length of four centimeters, the spotted darter is one of the medium-sized dragonflies.
It is easy to distinguish from other species due to the yellow-brownish basal spots on the hind wings. It can only be confused with the early darter ( S. fonscolombii ), where comparable basal spots can also be found, although they are much smaller there. In addition, the color of older spotted darter females occasionally fades with age.
.jpg)
Another feature in this case is the red-brown pterostigma , which in the early darter is light brown with a black border. An unambiguous distinction can be made by examining the genital morphology.
The color of the abdomen changes depending on the temperature and is more brownish in the male in cooler surroundings, but bright red in higher temperatures. The abdomen of the female is yellow to gray-brown. There are black median strips on the eighth and ninth segments of the abdomen of both sexes.
distribution
The spotted darter occurs in the Middle East and North Asia as well as in parts of Europe. The closed distribution area extends from Japan and Kamchatka via Siberia and southern Scandinavia to Central Europe . Although it is mainly found in the northern regions, it is also found in Portugal , northern Spain and Italy . In Great Britain she can often be found as a breeding guest flying in from northern France . In western France, however, the species is usually rarer.
The species can still be detected well above 1000 meters. The highest location in Germany was at an altitude of 1050 meters and in Switzerland at 2155 meters. For Carinthia , a natural distribution up to 1399 meters is given and in the Pyrenees there are finds of larval skins ( exuvia ) at an altitude of 2430 meters.
Habitat
.jpg)
The habitat of the spotted darter can be very diverse. It is often found in the area of smaller still waters overgrown with sedges . These are mainly sedge swamps with only a small proportion of open water surfaces and a high degree of cover for the sedges. Also silted up bank areas of shallow ponds, pioneer waters and wet meadows are popular. The areas can be in the middle of fallow land or agricultural areas. They are only rarely surrounded by forests or bushes, but almost without exception are exposed to the sun.
The reproductive waters are characterized by the fact that they have more or less strong water level fluctuations and the bank is very shallow. As a result, these waters often fall dry, especially in midsummer. In addition, there is grass-like vegetation that is largely covering. The spotted darter prefers to hunt in fallow meadows and fields near the water.
Larval habitat
The larvae live mainly in the shallow bank area of the reproductive waters at a depth of a few centimeters. The vegetation plays only a very subordinate role in their way of life, vertical stalks only use them when they leave the water to transform into the finished insect (imago). Even in waters with a slight current, the water in the larvae 's microhabitat is always largely immobile. The substrate mostly consists of sludge or residues of plant degradation materials ( detritus ). With regard to the chemical quality of the waters, the larvae are relatively undemanding and have a wide range of tolerance for most factors . This includes pH values from 4.5 to 9.3 as well as strongly varying ion concentrations and a fluctuating oxygen content . The larval waters are accordingly mostly classified as meso- eutrophic , that is, with a medium to high degree of organic pollution.
A regular change in the water level is obviously important for the development of the larvae of this species. A flooding of at least two months is necessary for larval development. In particular, flooding of large areas in early summer leads to optimal reproduction numbers for the animals, and in some years to mass reproductions.
Way of life
Flight times
The flight time of the dragonflies lasts from mid-May to the beginning of October, whereby they appear a little later in higher altitudes than in lower altitudes. The emergence , i.e. the transformation of the larvae into adults and the associated leaving the water, does not normally take place synchronously. In some years, however, there are regional mass occurrences of the animals, in which thousands of individuals of the species hatch within a few days. These mass occurrences depend on the occurrence of floods in early summer and in previous years when a relatively large number of dragonflies were already present. Especially in midsummer, the animals stay at the water in the morning hours and leave them around noon to hunt in the area.
After leaving the larval shell ( exuvia ), the newly hatched dragonflies spend most of their time in the immediate vicinity of the developing waters , mostly in the vegetation of neighboring fallow and swamp meadows. The hunting areas, on the other hand, can be a little further away from the water. The animals prefer sunny and sheltered places for hunting, especially meadows and grain fields. Sun-exposed plant stems serve as resting places, where they can also come together to form larger collections.
behavior
In some areas, and especially in years with mass reproduction, this species tends to aggregate , in which large numbers of animals gather in one place and rest or sunbathe together. These are not yet sexually mature young dragonflies. After a few days these accumulations dissolve with the onset of sexual maturity. Up to 80 animals per square meter were recorded during counts.
Like other dragonflies, the spotted darter use the morning sunlight to warm up their flight muscles. You can shorten this process by vibrating your wings. The animals hunt insects in flight, but also attack flower-visiting insects, especially on white and yellow flowers.
Mating and laying eggs
When looking for a partner, the males mainly fly over the dry areas of the silting zone of the water, more rarely they fly over the edges of the open water surface. Mating is initiated at the water and then continued in the neighboring vegetation, with the pairs settling in the vegetation at a height of about 20 centimeters. The actual mating takes about 15 to 20 minutes. After mating and the disintegration of the mating wheel, the animals form the mating tandem, typical for darter, in which the males grab the females with the cerci behind the head and both animals fly together.
The eggs , which do not have a gelatinous shell, are thrown in tandem flight over dry and lightly overgrown ground that is occasionally flooded, or over wet meadows . Eggs are only very rarely laid over shallow water areas.
Larval development
The larvae only hatch from the eggs when they are in the water; on dry ground the eggs can probably survive two winters. In the case of eggs laid by the beginning of August, larvae hatch if they come into contact with water in the same year, while eggs laid later generally overwinter. The development from hatching to emergence normally takes eight to ten weeks, but under optimal conditions it can also take place much faster and be over after four weeks. Eight to eleven moults occur during development.
After their development is complete, the larvae usually leave the water between June and August to emerge . The larval skins ( exuvia ) can be found in the bank area of the water, often on stalks of sedges (e.g. two-row sedge , Carex disticha ), the common rush ( Eleocharis palustris ) and the meadow foxtail ( Alopecurus pratensis ).
Hazard and protection
While the species used to be common, it is less common today due to the increasing destruction of its biotopes . In Germany it is classified as endangered in the Red List (1998), in some federal states it is even threatened with extinction. Like all dragonfly species, it is under strict conservation . The situation is similar in Austria and Switzerland . The species is considered endangered in Carinthia , but in the Vienna area as "Critically Endangered" and in the whole of Switzerland as "Endangered". Because of its increasing endangerment, the spotted darter was named Dragonfly of the Year in 2015 by the Society of German-speaking Odonatologists and the BUND in Germany .
The decline in biotopes is primarily due to the increasing drainage of floodplain meadows as well as to the development or intensive agricultural use of these areas. In some areas, however, the constant lowering of the groundwater level is the decisive factor in the complete drying of their habitats.
Despite the relative insensitivity of the larvae to water eutrophication, the increasing discharge of nutrients through intensive agricultural use in the vicinity of the water or the discharge of waste water can also be a cause of the decline in dragonflies in these water bodies. As a result of this change, the sedges are displaced by large reed species , such as the reed ( Phragmites australis ) or the cattail ( Typha sp.). Water bodies with high degrees of cover for these plants are no longer used by the animals, as there are no more shallow water areas exposed to the sun. This applies not only to the populations of the spotted darter, but also to those of other dragonfly species, especially the glossy rush damsel ( Lestes dryas ), or even the populations of amphibians such as the common frog ( Rana temporaria ) and the tree frog ( Hyla arborea ).
The main protective measures required are to maintain the water dynamics of the developing waters with regular flooding. This can only be achieved if there is no intervention in the water balance in the area, which can lead to a lowering of the water level. Large reeds should be pushed back by mowing , and an increased input of nutrients should be prevented. The developing waters of the dragonflies are very rarely in nature reserves , so that there is a need for a protection status here. In some federal states, evidence of larger populations of the spotted darter and the glossy rush damsel is sufficient as an argument for protection status.
literature
- Heiko Bellmann: Observe dragonflies - determine . Naturbuch Verlag, Augsburg 1993, ISBN 3-89440-107-9 .
- Gerhard Jurzitza: The Kosmos dragonfly guide . Franckh-Kosmos Verlag, Stuttgart 2000, ISBN 3-440-08402-7 .
- C. Röhn, J. Kuhn, K. Sternberg: Sympetrum flaveolum (Linnaeus, 1758) - Spotted darter. In: K. Sternberg, R. Buchwald (Ed.): Die Libellen Baden-Württemberg. Volume 2: Dragonflies (Anisoptera). Ulmer, Stuttgart 2000, ISBN 3-8001-3514-0 , pp. 548-559.
Individual evidence
- ↑ The Spotted Darter is Dragonfly of the Year 2015 , BUND press release from December 15, 2014. Accessed December 27, 2014
Web links
Fire Dragonfly (2011) | Teal Maiden (2012) | Spear Azure Maiden (2013) | Little Moss Maiden (2014) | Spotted Darter (2015) | Common Binsenjungfer (2016) | Common Wedgeon (2017) | Dwarf Dragonfly (2018) | Spotted Darter (2019)
