Banded demoiselle
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Banded demoiselle ( Calopteryx splendens ), male |
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| Calopteryx splendens | ||||||||||||
| ( Harris , 1782) |
The banded demoiselle ( Calopteryx splendens ) is a species of dragonfly from the family of the demoiselle (Calopterygidae). It inhabits slow-flowing streams, smaller rivers and canals rich in herbs, which are not too polluted and have sufficient sun. In addition to the blue-winged demoiselle ( Calopteryx virgo ), it is the only species of the demoiselle that can also be found in Central Europe and occurs here a little more frequently than these. The fluttering, fluttering flight style , more reminiscent of butterflies than dragonflies, is unmistakable for this family, as are the colored wings. The scientific species name Calopteryx splendens , formed from Greek and Latin , means something like "shiny beautiful wing". In Switzerland, the species was chosen as Animal of the Year 2008.
features
The fully developed animals ( adults ) of the banded demoiselle reach a wingspan of 6.5 to 7 centimeters and a body length of about 5 centimeters. This makes them one of the largest Central European dragonflies (Zygoptera). Males and females differ significantly: the males have an iridescent dark-blue-green colored body, and the greenish tinted, translucent wings each have a wide black-blue band that leaves out both the wing base and its tip. A Flügelmal ( Pterostigma ) lack. In addition, the three rearmost segments of the abdomen are white underneath (“white tail light”). The less conspicuous females are metallic green to bronze in color and have greenish tinted wings (without transverse ties) with equally greenish veins. When colored, they also have a white, so-called false wing mark on each wing tip (“false” because, in contrast to the pterostigma of other dragonflies, it has veins running through it). Females of the banded demoiselle, especially those that have just hatched, cannot always be clearly distinguished from those of the blue-winged demoiselle, which overall have somewhat brownish and slightly wider wings.
The larvae of the banded demoiselle develop over 10 to 12 stages. Compared to the larvae of other dragonflies, those of the demoiselle have a somewhat different, relatively easily recognizable appearance. These include a significantly shortened central gill leaf at the end of the abdomen and noticeably long first antennae. From the larvae of the blue-winged demoiselle (see also there) those of the banded demoiselle can only be distinguished in details. So here the first antennae is almost twice as long as the others, the middle gill leaf is slightly wider than the two outer ones and all gill leaves have two light-colored transverse bands.
distribution
The distribution area of the banded demoiselle is Palearctic and extends with several subspecies from the Atlantic to China. However, it is not closed, but sometimes includes disjoint sub-areas. In Europe, the distribution center is in the Mediterranean (with the exception of most of the islands); in Scandinavia the area ends at 64 ° 20 'north latitude and thus further south than at Calopteryx virgo . The 15 ° or 16 ° C July isotherm is a limiting factor . The nominate form of the species is also widespread in Central Europe; within eastern Germany there should also be an overlap and hybridization zone with the more easterly distributed subspecies Calopteryx splendens ancilla . Another subspecies Calopteryx splendens caprai colonizes central and northern Italy, the south of the Swiss canton of Ticino and the Mediterranean regions of France.
The main areas of occurrence are in lowlands such as floodplains and stream valleys.
Habitat and way of life
Banded dragonflies colonize the rather sluggishly flowing middle and lower reaches of rivers, alternatively also similarly structured ditches. It is important to have a higher degree of sunshine in the water and sufficient weeds with aquatic and bank plants. The species is considered to be a little more warmth-loving than the blue-winged demoiselle, which prefers the upper to middle reaches of smaller streams and tolerates a higher degree of shadowing of the waters as well as cooler conditions in summer.
However, there is also a greater overlap of the ecological requirements of both species, so that they can sometimes occur syntopically next to each other, especially with high abundance . In such cases, an ecological niche, i.e. an avoidance of competition, takes place via the time factor, as Calopteryx virgo shifts its flying season backwards. Forest areas and boggy, dystrophic flowing waters are avoided by the banded demoiselle. On the other hand, it is considered to be somewhat more tolerant of water pollution and a somewhat lower oxygen content in the water and can occasionally even be found in still waters. However, even larger accumulations of adults in a body of water do not automatically allow the conclusion that it is a reproductive habitat. Instead, it could be in the vicinity of the site.
All year round water-bearing rivers from about one meter wide with an open center as well as reed beds at the edges, in particular those made from reed grass or water swaths , are populated with greater steadiness. Regionally, for example in northern German floodplains, populations of arrowheads with flooding hedgehog reeds favor settlement. The leaves sticking out of the water are often used as a landing area.
Reproductive behavior
The males of the banded demoiselle claim territories along the course of the stream and show pronounced territorial and courtship behavior. The districts are on average about 2.6 to 3 m long and 90 cm wide; however, in populations with a very high individual density there is also a male every few decimeters. In addition, many males cannot find unoccupied territories suitable for laying eggs and stay at the territorial boundaries of other males. If a female flies into the territory of a male, this begins with a courtship. It flies towards the female with a conspicuous hovering flight and shows it its "white tail light" with its abdomen bent upwards. In this way the male guides the female to an egg-laying place. There it circles the courted girl again with its pendulous soaring flight . If the female then remains in place, the male sits on the female's wings and attaches itself to him with his abdominal appendages in dragonfly fashion.
This is followed by copulation, which takes around two and a half minutes on average. The mating wheel then loosens again and after a period of rest the female begins to lay eggs by piercing the eggs (10 to 22 per minute) into aquatic plants near the surface of the water. To do this, the animal can submerge completely, always doing so head first. Meanwhile, the male continues to defend his territory against other members of his sex by means of threateningly spread wings and by approaching competitors. In a favorable territory, up to ten copulations per day with different females can occur.
The embryonic development in the eggs takes about six to nine weeks in Central Europe, then the larvae hatch.
Larval and emergence habitat
The dragonfly larvae need underwater vegetation that protrudes into the current and offers them good support. This function can also be taken over by the roots of trees that have been washed away. However, places to stay at the foot of brook reeds (reed grass, hedgehog cob) or within stocks of herbaceous diving leaf plants such as waterweed , water star or flooding water cockfoot are particularly typical . With regard to the water depth, a broad spectrum from a few centimeters to several decimeters is used, depending on the local conditions of current and light. The flow speed of the larval waters is between 2 and 70 cm / s, the optimum being 3 to 30 cm / s and the flow behavior must be as uniform as possible.
Demoiselle larvae generally avoid the water bed; in most habitats of the species, however, at least portions of rather fine-grain substrates such as sand, loam or peat mud are observed. The oxygen content in rivers should not fall below values of 6 to 7 mg / l in the long term. The species also shows greater tolerance towards other water-chemical parameters than, for example, the blue-winged dragonfly. When it comes to the water temperature, on the other hand, there are higher demands: In the larval habitat, mean summer temperatures of 16 to 24 ° C are optimal.
Larvae of the banded demoiselle stay with a relatively small radius of action on the underwater structures described. By changing their posture, they adapt to the respective flow and oxygen conditions. They defend their seat against conspecifics. They lurk for small insect larvae that pass by, such as the mosquitoes and black flies, as well as small flea shrimp , which they catch and eat with a special catch. Their lifespan as a larva depends on the habitat and weather conditions. In warm lowland streams and ditches, an annual cycle is usually observed; in cooler (mountain) streams a two-year development period. In the year before metamorphosis , the larvae go to winter in the penultimate or last larval stage.
(For further details on the individual development of the larvae, see the blue-winged demoiselle ; both species are similar in this respect.)
At the end of their development, the larvae finally climb stalks and other vertical structures directly on the bank of the water in order to moult there at heights of five to 40 (occasionally more) centimeters above the waterline to form the imago. In Central Europe this happens from the end of April / beginning of May and lasts well into July, the peak of emergence (imaginal moulting) is between the end of May and mid-June.
Habitat of maturity, hunting and resting of the adults, time of flight
After hardening, the newly hatched adults swarm out into the surrounding area, where they hang out in meadows and on the edges of forests and hunt for small insects. They have matured within ten days, with sexual maturity occurring after three days. The now colored and adult animals return to the slip waters. The flight time of the mature banded demoiselle lasts from mid-May to early September, with a peak from mid-June to early August. In the reproductive waters they are only active at temperatures of at least 16 ° C. During the day they stay at the water from the morning (compare “reproductive behavior”), while at night they seek resting places, which for males can be 20 to 40 m away from the water, for females up to 70 m. These are stocks of dense herbaceous vegetation, such as reeds, uncut meadows or even grain fields. Occasionally sleeping communities are formed from dozens of individuals, mostly males. Cheap resting places are always sought out. The activity and life period as a finished dragonfly only lasts an average of about two weeks individually - individual, marked females could also be found for up to 50 days, and males after a maximum of 69 days. During this time, most of the animals hardly move more than 400 meters from the hatching site. Occasionally, however, expansion flights several kilometers wide can also be registered.
Predators
The life expectancy of dragonflies is limited by a wide variety of factors, including numerous predators in all life stages. The larvae in the water and even the females who submerge to lay their eggs are preyed on by fish, sometimes also by predatory insects such as back swimmers , water striders , larger dragonfly larvae as well as yellow scotch beetles and their larvae. Birds living near water such as herons , storks , kingfishers , ducks and various songbirds sometimes hunt dragonfly larvae in a targeted manner. The adults - especially the newly hatched, still maturing ones - are preyed on by many songbirds (for example brook and mountain wagtails , warblers and swallows , but also by larger bird species) as well as by dragonflies and spiders , among others .
Endangerment and legal position
The populations of the banded demoiselle have declined in many places, in particular due to pollution, canalisation and intensive "maintenance" of flowing waters. Far-reaching hydraulic engineering measures such as straightening, piping, bank construction and damming rivers have severely restricted the habitats of this dragonfly; the remaining biotopes are often impaired by sewage discharges, fertilizer and pesticide inputs as well as interventions such as the mowing of bank vegetation, which sometimes takes place in summer, and weed removal of the water body.
The world population is classified as Least Concern by the International Union for Conservation of Nature IUCN in the 2009 edition of the Red List of Threatened Species . Since it reacts a little less sensitively to anthropogenic environmental changes than the blue-winged demoiselle, it is listed in the current Red List of Germany as a kind of "warning list"; in many federal states, however, it is already considered endangered. In four federal states of Austria the species is classified as “potentially endangered” or “endangered”. In the Red List of Threatened Species in Switzerland, the nominate form of the species is listed as "not endangered" and the subspecies Calopteryx splendens caprai, which has never been common in Switzerland, is listed as "potentially endangered".
In Germany it is under nature protection; in the Federal Species Protection Ordinance, like all species of the order dragonflies (Odonata) in Appendix 1, it is listed as a specially protected species and is accordingly also specially protected under the Federal Nature Conservation Act.
swell
- Heiko Bellmann: The cosmos dragonfly guide. Franckh-Kosmos, Stuttgart 2007, ISBN 978-3-440-10616-7 .
- Klaus Sternberg & Rainer Buchwald: Calopteryx splendens (Harris, 1782), banded demoiselle. S. 187–202 In: Sternberg / Buchwald (ed.): Die Libellen Baden-Württemberg. Volume 1. Ulmer, Stuttgart 1999, ISBN 3-8001-3508-6 .
Individual evidence
- ↑ Alain Maibach: Species Protection Sheet, pages 1-11. (PDF; 714 kB) (No longer available online.) In: Universität Neuchâtel UniNE. Archived from the original on November 14, 2005 ; Retrieved December 23, 2009 .
- ↑ Klaus Sternberg: Enemies, Parasites and Commensals. S. 156–171 in: Sternberg / Buchwald (ed.): Die Libellen Baden-Württemberg , Volume 1. Ulmer, Stuttgart 1999, ISBN 3-8001-3508-6
- ^ Federal Agency for Nature Conservation, Bonn: Red List of Endangered Species in Germany. (No longer available online.) Archived from the original on March 1, 2016 ; accessed on December 23, 2009 (“PDF file; 447.34 MB”). Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Federal Environment Agency Austria: Red List of Endangered Animal Species in Austria. In: Austrian Species Protection Information System OASIS. Retrieved December 26, 2009 .
- ↑ Red list of endangered species in Switzerland: dragonflies. In: Federal Office for the Environment FOEN from 2002. Accessed on December 23, 2009 .
- ↑ Appendix 1 of the Federal Species Protection Ordinance
- ↑ Banded dragonfly at www.wisia.de
Web links
- www.pronatura.ch: Banded demoiselle - Animal of the year 2008
- Calopteryx splendens at Fauna Europaea
- Calopteryx splendens in the endangered Red List species the IUCN 2009. Posted by: Clausnitzer, V., 2007. Retrieved on December 21 of 2009.
- Macro shots of the banded demoiselle
- Videos on Calopteryx splendens published by the Institute for Scientific Film .
Tree Frog (1998) | Beaver (1999) | Lynx (2000) | Golden Eagle (2001) | Wood ant (2002) | Swallowtail (2003) | Brown Hare (2004) | Sand lizard (2005) | Alpine Ibex (2006) | Grayling (2007) | Demoiselle (2008) | Brown Bear (2009) | Eucera longicornis (2010) | Earthworm (2011) | Brown Long-eared (2012) | Midwife Toad (2013) | Feldgrille (2014) | Grass snake (2015) | Water shrew (2016) | Red Deer (2017) | Ermine (2018) | Fireflies (2019)
