Spear Azure Maiden
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Spear damsel ( Coenagrion hastulatum ), male |
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| Coenagrion hastulatum | ||||||||||||
| ( Charpentier , 1825) |
The spear damsel ( Coenagrion hastulatum ) is a species of dragonfly from the family of the slender dragonflies (Coenagrionidae), whose range extends from Central Europe to Eastern Siberia, and which is the most common of the blue slender dragonflies in its distribution focus in the boreal northern Europe and North Asia. C. hastulatum is a typical bog species that inhabits nutrient-poor waters with well-developed, structurally rich silting zones, but can also be found in nutrient-rich small bodies of water in Northern Europe and Russia.
The Spear-Azurjungfer was chosen jointly by BUND and the Society of German-speaking Odonatologists in 2013 and 2020 as " Dragonfly of the Year " in order to draw attention to the increasingly difficult living conditions and the decline in numbers of these dragonflies.
features
Characteristics of the adults
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Within the Azurjungfer , the spear-Azurjungfer is a typical but rather small representative with a body length of 31–33 mm and a length of the hind wings of 16–22 mm. The males have a pale blue, slightly turquoise playing base color and can be completely green on the underside, especially on the underside of the eyes. The front part of the body ( thorax ) is marked with black markings, typical of the azur maiden. In the middle of the top there is a wider black median stripe, this is flanked on both sides by the light ante-humeral stripes and the subsequent black humeral stripes. The light blue sides of the thorax underneath are structured by two clearly defined, shorter black lines extending from the base of the wing. The segments of the abdomen are also typically drawn for azure maidens. On the second segment there is a characteristic arrow-like or mushroom-shaped drawing, which is flanked by two black lines on the side. However, it is quite variable and therefore cannot be used for determination alone. The third segment is drawn in a characteristic shape with a spearhead extending from the end of the segment, while significantly less than half of segments three and four are blackened. On the other abdominal segments of the male adults, the black drawing then takes up more space, segments seven and ten are completely blackened, the eighth and ninth, on the other hand, are completely blue and thus form a noticeable “bottom light”.
The females are more powerfully built; the black drawing of the abdomen, each pointed towards the anterior segment joints, is more extensive than that of the males and covers almost the entire upper surface. There are two color forms, the more common yellowish-green ventrally whitishly pollinated heterochromic form (colored like the females) and a rarer androchrome (similar to the males colored) light greenish-blue form.
Shortly after the transformation to the imago , the dragonflies are still without a drawing - this only develops within the next few hours. The typical blue or green color is also only formed during maturation in the following days.
Similar species
Males of the spear maiden resemble other species in the genus. If the drawing of the second abdominal segment does not have a stem, it can easily be confused with the lunar azure maiden ( Coenagrion lunulatum ), whose drawing only consists of a semicircle with two side lines. With this, however, no narrow line is formed between the postocular spots on the body-facing side of the compound eyes and the abdominal segments three to six are blackened to a large extent, so that the rear part of the abdomen appears completely black except for the taillight. A reliable differentiation can be made on the basis of the male abdominal appendages, the details of which can be perceived when viewed from close up. The upper abdomen appendages are shorter in the spear-azure maiden than the lower ones, while the upper and lower ones in the moon-azure maiden are the same length.
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Also not easy to distinguish from Coenagrion hastulatum are the similar males of the horseshoe damsel ( Coenagrion puella ) and the bat damsel ( Coenagrion pulchellum ). Here, however, the abdominal segments are only slightly blackened and the lower abdominal appendages point upwards in a characteristic way in the lateral view , whereas in C. hastulatum they point slightly downwards.
The females of the spear azure maiden are practically identical to the females of the horseshoe azure maiden and can only be distinguished by the shape of the prothorax and its typical shape of the posterior margin. In the case of Coenagrion hastulatum , this is formed from two straight lines that run obliquely to one another and meet at one point, like a flattened "V". In Coenagrion puella the rear edge is wavy and forms three very flat arcs. In the females of the lunar azure maiden, this area is characterized by two large indentations and thus clearly different; The abdomen is also predominantly blackened dorsally, similar to the spear-azure virgin, but interrupted by a characteristic light part in the front part of the eighth abdominal segment.
Characteristics of the larvae
The length of the larvae is 14–15 mm, that of the gill leaflets an additional 5–6 mm. The coloring is variable, mostly the larvae are brownish to greenish in color. In contrast to the seven segments of the antennae of the head of Coenagrion puella and C. pulchellum , the antennae in C. hastulatum have only six segments. The typical spots on the back of the head are regular and widely distributed, and the abdomen is also spotted, but not very clearly. The femora are banded once shortly before the joint to the tibia . Most of the flattened gill leaflets have a dark, narrow cross-band in the middle, which is reinforced by clear notches on the outer edges, so that the gill leaflets appear to be divided into two parts. The edge of the proximal part is lined with small bristles, that of the distal part with dense, very fine hairs. Some specimens also have one or two more narrow ties to the rounded tip.
The spear damsel larva is similar to other common dragonfly larvae found in the same habitat. The clear spots on the back of the head distinguish them from the larvae of the common mugwort ( Enallagma cyathigerum ) and the great pitch dragonfly ( Ischnura elegans ). The larvae of the horseshoe and bat azur damsel are also very similar, differ not only in the number of segments of the antennae but also in the lack of the central band of the gill leaflets. It is very difficult to distinguish the only slightly larger larva of the moon azure maiden. It also has six antenna segments and the formation of the gill leaflets is identical. The pattern of spots on the back of the head is, however, more inconsistent and more sparsely developed at the edges than on the Spear-Azurjungfer.
distribution and habitat
distribution
The spear damsel is the most common of the blue slender dragonflies in large parts of boreal Europe, the occurrence breaks down into disjoint relic populations at the southern limit of distribution . The distribution area extends from Central Europe to the Lena in eastern Siberia and in the southeast to the Chinese province of Jilin . The focus is on northern Europe and northern Asia, the northern extension extends to the polar sea . The western limit of distribution stretches from the Benelux countries over the Vosges to the western Alps , three further west lying sub-areas in Scotland , in the Massif Central and in the Pyrenees are interpreted as relics of a western advance in the outgoing preboreal . The southern limit of distribution runs from the southern edge of the Alps in south-eastern France, northern Italy and northern Slovenia over the northern Carpathian arch further east.
In the German-speaking area, the species is only quite common in northern Germany; there are still larger occurrences in northern Bavaria.
habitat
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C. hastulatum is a typical type of bog that inhabits nutrient-poor waters with a well-developed, structurally rich silting zone. The 30–70 cm high vegetation made up of large sedge or similar species is important for the species. If this is missing, the population density of the spear-azure virgin drops significantly or the species does not exist at all. A pure floating leaf and swinging lawn vegetation is not flown over, it is only populated if it is interspersed with beaked sedge .
In contrast to the current literature, K. Sternberg and C. Röhn do not classify the spear-azure virgin as a typical bog species, which therefore does not have a strict connection to dystrophic bogs, but only shows a certain preference for them and in Central Europe does not fly more frequently on nutrient-rich small bodies of water because here the silting zones have disappeared due to overexploitation and destruction. Such a colonization can not only be observed in the boreal zone of Northern Europe, but is also expected for the distribution center in Russia and Siberia, from where no information is available. A temperate continental climate with cold winters and warm summers is preferred , as is particularly the case in moor waters.
Danger
The stock of Coenagrion hastulatum is declining in parts of its central European areas, but it is still common and widespread in northern Eurasia, therefore classifies International Union for Conservation of Nature and Natural Resources (IUCN) Coenagrion hastulatum as uncritical ( least concern a) . For Germany, the Speer-Azurjungfer is classified for the first time as "critically endangered" in the new Red List, which will appear in 2013. Intensive agriculture with the associated high nutrient inputs into bodies of water, as well as their drying out due to excessive water abstraction, as well as climate change are held responsible for the decreasing stocks.
Way of life
The flight time of the adults in the flatlands of Central Europe is between May and July, with the highest abundance from mid-May to the end of June. In colder regions of Northern Europe, C. hastulatum flies until September; as well as populations in the highlands are delayed by up to two weeks. The phenology is also strongly influenced by the weather, so hatching in the same biotope can occur 4–6 weeks later in cold years than in warm years.
As resting habitats, clearings in the bog forest and meadows in the edge area of the forests, in which the dragonflies sit in the vegetation at a height of 20–40 cm, usually serve not more than 50 m from the development water. They become active as soon as their resting places are exposed to the sun. C. hastulatum is comparatively shy and flies open when approaching.
Reproduction
Reproductive pairs are often found in the morning in the resting or foraging habitats and appear in tandem at the developing waters, where the males await unmated females in the transition area between the open water zone and the bank vegetation. The actual mating takes 15–30 minutes and takes place as long as the habitat is sunny.
Eggs are usually laid with the male attached, which initially stands vertically above the female, but then often settles down. If the female goes under water in order to continue piercing the eggs into the vegetation, the male often only dips halfway into the water and then loosens the connection, in which case the female continues laying eggs on her own. The Submersablage but can also be carried out with coupled males, both for climbing up to 50 cm deep into the water and can remain submerged for 23 minutes up. This can be repeated several times in a row, each interrupted by a break of several minutes. Eggs are usually laid some distance from the bank in dead or living vegetation; leaves and stalks of sedges or cottongrass are preferred over rather flat substrates such as flooding water lily leaves .
Larval development
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Embryonic development takes 2–3 weeks. The nimble larvae, which quickly swim away when disturbed, lurk immobile for prey when there is good food supply, but actively search for food when there is less prey density. When a predator approaches, the larvae behave calmly and press themselves closely to the substrate. Under optimal development conditions, densities of up to 250 larvae per square meter can be achieved.
Astatic - that is, only temporarily existing - small bodies of water are colonized by the Speer-Azurjungfer; the larvae can survive dry periods in their developing waters of up to three and a half months. If the water falls dry, the larvae retreat under the sheets of the previous year's vegetation that are glued together, under which the mud remains moist even when it is dry. Larvae were found which at the end of the dry period were trapped in the almost dried-out, viscous mud and looked like dead, but quickly recovered when put in water.
The number of stages, i.e. the number of moults between the different larval stages, can be between 10 and 13. Hibernation usually takes place in the last larval stage, development is univoltin , so it takes a year for the development cycle of a generation. In cooler waters, development can be delayed - up to four years in the north of the range.
Hatching takes place preferably in sunny flat bank areas in the morning hours, but can continue into the evening. The larvae hatch on vertical vegetation, usually just above the water level so that the gill leaflets are still submerged. Individuals hatching early in the year are usually heavier and have a wider head than those of later emergence.
It takes about a week for the males to reach sexual maturity, but the first mating wheels can only be observed 18 days later. This could possibly be explained by the longer maturation phase of the females. Juvenile individuals show a certain tendency to migrate from developing waters and thus to support the spread of the species, while older specimens are locally loyal. In large numbers, the spear azure maiden can displace the widespread and common horseshoe azure maiden.
Systematics
Coenagrion hastulatum is placed within the slender dragonflies in the genus of the azure maiden ( Coenagrion ), which was created in 1890 by William Forsell Kirby . The genus, numbering forty species, is mainly found in Europe and Asia, three species are represented in North America.
The spear-azure maiden was first described by Toussaint von Charpentier as Agrion hastulatum in 1825 . The specific epithet hastulatum is derived from the Latin word "hastulatus" for 'with a small spear (marked)' and describes the characteristic drawing of the second abdomen segment of male adults, which is said to resemble a spear or the spearhead. The German species name also relates to this.
swell
literature
- Klaus Sternberg, Rainer Buchwald (ed.): The dragonflies of Baden-Württemberg. Volume 1: General part, dragonflies (Zygoptera). Verlag Eugen Ulmer, Stuttgart 1999, ISBN 3-8001-3508-6 .
- Klaas-Douwe B. Dijkstra: Field Guide to the Dragonflies of Britain and Europe. British Wildlife Publishing, Gillingham 2006, ISBN 0-953139948 .
- Heiko Bellmann: The Kosmos dragonfly guide. Determine the species of Central Europe with certainty. Franckh Kosmos Verlag, Stuttgart 2007, ISBN 978-3-440-10616-7 .
- Gerhard Jurzitza: The Kosmos dragonfly guide . The species of Central and Southern Europe. Franckh Kosmos Verlag, Stuttgart 2000, ISBN 3-440-08402-7 .
- Steve Cham: Field Guide to the larvae and exuviae of British Dragonflies. Shrewsbury, The British Dragonfly Society, Peterborough 2012, ISBN 978-0-9556471-2-3 .
Individual evidence
- ↑ a b BUND : The Speer-Azurjungfer is "Dragonfly of the Year 2013" [1] , accessed on February 20, 2013.
- ↑ BUND press release: "The Spear-Azurjungfer is Dragonfly of the Year 2020"
- ↑ a b c d e Klaas-Douwe B. Dijkstra: Coenagrion hastulatum (Charpentier, 1825). In Dijkstra: Field Guide to the Dragonflies of Britain and Europe , p. 114.
- ↑ a b c d e f g h i K. Sternberg, C. Röhn: Coenagrion hastulatum (Charpentier, 1825). In Sternberg, Buchwald: The dragonflies of Baden-Württemberg. Volume 1 , pp. 237-246.
- ↑ a b Klaas-Douwe B. Dijkstra: Coenagrion lunulatum (Charpentier, 1840). In Dijkstra: Field Guide to the Dragonflies of Britain and Europe , p. 115.
- ↑ Steve Cham: Field Guide to the larvae and exuviae of British Dragonflies , pp. 70-71.
- ↑ Xin Yu, Wenjun Bu: Chinese damselflies of the genus Coenagrion (Zygoptera: Coenagrionidae) . In Zootaxa, ISSN 1175-5334 ( Download ; PDF; 968 kB).
- ^ Coenagrion hastulatum in the IUCN Red List of Threatened Species 2012.2. Posted by: V. Clausnitzer, 2009. Accessed February 20, 2013.
Web links
Coenagrion hastulatum at Fauna Europaea
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)