Coenagrion angulatum
| Coenagrion angulatum | ||||||||||||
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| Scientific name | ||||||||||||
| Coenagrion angulatum | ||||||||||||
| Walker , 1912 |
Coenagrion angulatum is a species of dragonfly from the family of the common dragonfly (Coenagrionidae), which is widespread in Canada and in northern North America andcan be very commonin the prairie areas . Sunny, heavily overgrown ponds, lakes and swamps as well as slow-flowing brooks that freeze over in winter are settled. The larvae, protected by anti-freeze substances in the blood, can be frozen in the ice for wintering. Coenagrion angulatum is with Coenagrion interrogatum and Coenagrion resolutum one of three species of azure virgin found in America.
features
Characteristics of the adults
Coenagrion angulatum is a typical slender dragonfly with a body length of 27 to 33 millimeters and a length of the hind wings of 16 to 22 millimeters. The male adults have a blue base color, the pale greenish eyes are dark on top, so that they appear to be covered by a cap. The median strip on the upper side of the thorax is wide, the lateral ante-humeral and humeral strips are roughly the same width, but narrower than the median. The blue sides of the thorax underneath are structured by two fine black lines starting from the base of the wing, as is typical for azur maiden. The drawing on the top of the abdomen , with blue anterior and posterior segments and black central segments, is unmistakable. The second segment has a drawing typical of azur maiden in the form of a slightly curved horizontal stripe with two lateral lines, which can, however, also be missing. The drawing is sometimes described as reminiscent of a face with a mustache. Segments three to six are predominantly black with blue rings on the proximal segment joints, which are widest on the anterior segments and narrow towards the rear, so that the seventh segment is completely blackened. Segments eight and nine and the sides of the tenth are blue again.
The females are more powerfully built; the chest drawing corresponds to that of the male. The abdomen is completely black on top with narrow pale rings at the segment ends, somewhat wider and clearly blue in color in segments seven to nine. However, the side surfaces of the abdomen are noticeably pale and widen at the base of the eighth segment to form two distinct dorsal bruises. The females appear in two color morphs, a yellow-greenish to brown heterochromic (colored like the females) and a blue androchromic (male-colored) form.
Similar species
Coenagrion angulatum is more robustly built and darker blue than the two other azure virgin species found in North America. The male adults are difficult to confuse with other slender vials, in the area of distribution there are few other species whose anterior and posterior abdominal segments are blue, while the middle segments appear predominantly black. In the smaller Enallagma geminatum , whose distribution only overlaps slightly anyway, the upper side of the second and predominantly all segments three to eight are blackened, just like with Enallagma exulans , which lives in a different habitat and is slimmer. Pitch dragonflies occurring at the same time have a greenish thorax.
The females of Coenagrion angulatum can resemble those of Coenagrion resolutum , but are usually unmistakable due to the pale spots of the eighth segment. However, these may be missing here and there. A reliable determination is then possible via the prothorax and its typical shape of the posterior margin, which is three-lobed in C. angulatum , but not in C. resolutum . The blue-ringed abdomen of the female of Coenagrion interrogatum is much less blackened.
The females of Enallagma anna , Enallagma annexum , Enallagma boreale , Enallagma carunculatum , Enallagma civile and Enallagma clausum also have wider pale rings at the abdominal segment joints . The black drawing on the top of each abdominal segment is designed in the characteristic torpedo shape of the cup maids and thus differs from the straight-edged drawing of the azure maids. These typical bulges of the abdominal markings at the distal segment ends can also be found in Enallagma hageni and Enallagma ebrium , but are clearly less developed here. However, they lack the pale spots of the eighth segment and they have smaller postocular spots than C. angulatum . In addition, a color-contrasting, horizontal stripe in the middle of the eyes, which is missing in the azure maid, is typical for the females of the cup maids.
distribution
C. angulatum is a dragonfly found in boreal forests and the northern part of the Great Plains of North America and Canada. The distribution ranges from Alaska , northern British Columbia over the Canadian Prairie Provinces and Iowa to James Bay in the east.
The species can become very common in prairie wetlands, but also find suitable habitats in Aspen Parkland and southern boreal forests in open, sunny areas. Ponds, lakes and swamps are populated, as well as slow-flowing streams, which are mostly heavily overgrown and shallow enough to partially dry out.
Way of life
The males rarely fly over open water, but are more likely to be found in dense grass, where they feed on mosquitoes and small flies. With the beginning of the reproduction, for which the dragonflies form a mating wheel, the actual copulation takes place , which can take up to 20 minutes. Afterwards, the male, who is still attached, is laid in flood vegetation or in emerging submerged parts of the plant. To do this, the couple dives underwater together, where they can stay for up to 30 minutes and the female pierces 150 to 200 eggs into the living plant tissue. After laying eggs, the dragonflies can be found and fly away, still connected in tandem.
It takes two to three weeks for the larvae to hatch from the eggs, followed by rapid development before overwintering begins in one of the last three developmental stages. To do this, the larvae stop developing and, clinging to plant stems, they await frost or go to the bottom of the ice cover, where they can be frozen. In general, they are 15 to 20 cm below the surface of the ice. The larvae themselves do not freeze because they are protected by antifreeze substances in the blood that form in winter. These not only protect them from predators , but also represent an adaptation to the mostly shallow waters that predictably freeze through in winter.
The larvae remain in the diapause until the ice melts and then continue their development. After hatching, the newly hatched dragonflies leave the water to feed and mature. It takes about a week to develop into a sexually mature animal. Under adverse circumstances, semivoltine development can also occur, in which C. angulatum takes two years to complete the development cycle.
The adult flight time in Ontario and British Columbia falls in June, in Saskatchewan and Iowa it can begin as early as May and last until July.
Systematics
Coenagrion angulatum 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, which counts 40 species, is mainly found in Europe and Asia and is only represented in America by Coenagrion angulatum and Coenagrion interrogatum and Coenagrion resolutum . The latter two are more closely related to each other than to C. angulatum , which is also reflected in the choice of their habitats. They prefer raised bogs, whereas C. angulatum is rarely found here. The two species are also physically similar, but C. angulatum is much more powerfully built. All three species have relatives in the Old World , with whom they are more closely related than they are to each other.
The dragonfly species was first described in 1912 by Edmund Murton Walker , the epithet angulatum means "angled" and probably refers to the shape of the male abdominal appendages. The English name "Prairie Bluet" aptly describes the distribution center of the species in the North American prairie .
swell
literature
- John Acorn: Damselflies of Alberta, Flying Neon Toothpicks in the Grass. University of Texas Press, Austin 2011, ISBN 0-88864-419-1 .
- Dennis Paulson: Dragonflies and Damselflies of the East, Princeton Field Guides. Princeton University Press, New Jersey 2011, ISBN 978-0-691-12283-0 .
- Dennis Paulson: Dragonflies and Damselflies of the West, Princeton Field Guides. Princeton University Press, New Jersey 2000, ISBN 978-0-691-12281-6 .
Individual evidence
- ↑ a b c d John Acorn: Prairie Bluet. In Damselflies of Alberta , pp. 75-77.
- ↑ a b c d e f g Dennis Paulson: Prairie Bluet. In Dragonflies and Damselflies of the East , pp. 81-83.
- ↑ a b c B. C. Jones: Coenagrion angulatum on the website of the EH Strickland Entomological Museum of the University of Alberta . Retrieved April 9, 2013.
- ^ A b Dennis Paulson: Prairie Bluet. In Dragonflies and Damselflies of the West , pp. 73-74.
