Asiatic maidenhead
| Asiatic maidenhead | ||||||||||||
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Asiatic maidenhead ( Gomphus flavipes ), |
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| Systematics | ||||||||||||
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| Scientific name | ||||||||||||
| Gomphus flavipes | ||||||||||||
| ( Charp. , 1825) |
The Asian wedge damsel ( Gomphus flavipes ) is a species of dragonfly from the family of the river damsel (Gomphidae). Alternatively, the name Stylurus flavipes has also been suggested; However, it is controversial whether the genus rank is actually justified for the taxon Stylurus . This yellow-black colored dragonfly (Anisoptera) inhabits the middle and lower reaches of larger rivers, which are not yet overbuilt and canalized. In Central Europe it occurs only rarely, but despite the somewhat misleading German species name, it is an autochthonous , indigenous species. The scientific name, which is composed of Greek and Latin, means something like "yellow-footed wedge".
features
The species is built relatively slender in comparison to other wedge maids; it reaches a body length of 50 to 55 millimeters and a wingspan of 70 to 80 millimeters. In addition to black, the legs also have a greater proportion of yellow. A striking distinguishing feature from other Gomphus species is the drawing of the upper "chest" ( thorax ) - there are three black stripes on each side of the anterior thorax section that are equidistant from one another. Correspondingly, the yellow areas in between are also designed as stripes of roughly the same width.
In the adult male, the light body parts are pale yellow to slightly green, whereas in the female they are bright yellow. The rear abdomen is widened somewhat like a wedge in the males, but not as conspicuously thickened as club-shaped as e.g. B. the common wedge maiden . There is a possibility of confusion with various other maidenheads, including Gomphus pulchellus and Gomphus simillimus .
The larvae are recognizable from other gomphids by a very elongated abdominal tip. Their exuvia can therefore be identified quite reliably as a species.
distribution
The main distribution area of the species is in Eastern Europe and Asia. The nominate form occurs from Central Europe to Eastern Siberia - there is also an isolated subarea in southwestern France - to the south it occurs to northern Italy and northeastern Greece. A subspecies Gomphus flavipes lineatus colonizes Asia Minor, the Middle East and Central Asia, while a third subspecies, Gomphus flavipes sibirica , has been described for Eastern Siberia .
The western area boundary, i.e. in Central Europe, seems to be variable and to be characterized by current expansion advances to the west. For decades, the Asiatic maidenhead was considered to be extinct in West Germany, for example; only occurrences from the former GDR between the Elbe and the Oder were known. Even today, stocks on the Spree and Oder are particularly rich in individuals. In recent years, however, individual finds of the species have increased further west, for example on the Aller in Lower Saxony , various sections of the Rhine , the Weser , the Lippe and the Dutch Meuse . However, the Elbe can currently still be defined as the western border of the steady distribution area.
In Austria, the March from Baumgarten to the confluence with the Danube and the Danube floodplains near Regelsbrunn are home to the main occurrences of the species there.
Habitat and way of life
Larvae
The Asian wedge damsel inhabits the middle and lower courses of large rivers, where very fine-grained soil components such as sand, loam, clay and detritus sediments , sometimes also mud, predominate. Here the larvae need flow-calmed, bare, sun-exposed bays or sliding slope zones (alternatively also: groyne fields between groynes on partially built-up rivers). They often stay in shallow water near the shoreline and hide buried in the ground. They are primarily nocturnal and eat diatoms , tubeworms , mosquito larvae and other prey within the sediment , which they track down by actively searching by touching the antennae (optical perception does not matter). The larvae usually have a three-year, regionally four-year development period, whereby they go through 14 molting stages.
Adults
The emergence (imaginal moulting), i.e. the hatching of the transformed adults , begins in Central Europe at the turn of the month of May / June and sometimes does not end until August. It takes place unsynchronized over a longer period of time. The flight time lasts until September (October).
The hatch sometimes takes place just a few centimeters from the waterline on structures of all kinds (plants, driftwood, stones, etc.). Because of their proximity to the water, the animals that are just hatching are sensitive to waves, such as those caused by ship traffic. In this phase, however, many of them also become prey for birds, particularly stilts . The hatching process takes between a quarter of an hour and an hour and is therefore very short for a dragonfly.
After hatching, the young adults leave the water area and distribute themselves in a radius of several kilometers in the surrounding area during a two-week maturation period. As sexually mature animals, they return to the water. Here they prefer to stay close to the water on sunny sandy shores. Their lifespan is given as 30 to 40 days.
Mating begins in flight and ends after five to 25 minutes of sitting. The female then flies alone over the water surface at a height of 20 to 30 centimeters, scraping off the eggs in rhythmic movements. These sink to the bottom of the water and stick to the sediment with the help of their sticky jelly.
Danger
According to the European Habitats Directive and the German Federal Nature Conservation Act, the Asian Keiljungfer is a "strictly protected" species. Due to its close connection to undeveloped or only moderately developed rivers with natural water and flow dynamics and near-natural, unpaved bank structures, it is wide Parts of Central Europe have become very rare or have completely disappeared. Water pollution, water management maintenance measures as well as boat and ship traffic causing waves have also contributed to the decline in Gomphus flavipes and are still among the risk factors.
In western Germany, the species was considered to be extinct for decades in the 20th century, while in eastern Germany there are still very abundant populations.
swell
literature
- Heiko Bellmann: The Kosmos dragonfly guide . Franckh-Kosmos Verlags GmbH & Co., Stuttgart 2007, ISBN 978-3-440-10616-7
- Klaus Sternberg, Bernd Höppner, Franz-Josef Schiel & Michael Rademacher: Gomphus flavipes (Charpentier, 1825) - Asian maiden wedges. P. 285–293 in: Sternberg / Buchwald (ed.): Die Libellen Baden-Württemberg. Volume 2: Dragonflies (Anisoptera). Ulmer, Stuttgart 2000, ISBN 3-8001-3514-0
Individual evidence
- ↑ Information on the FFH type Asian Keiljungfer in NRW
- ↑ www.vielfaltleben.at: The Asiatic Maidenhead ( Gomphus flavipes ) in Austria
