Coenagrion resolutum
| Coenagrion resolutum | ||||||||||||
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Couple laying eggs |
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| Coenagrion resolutum | ||||||||||||
| ( Hagen in Selys , 1876) |
Coenagrion resolutum is a species ofdragonflyfrom the family of slender dragonflies (Coenagrionidae), which occurs in large parts of Canada and North America and is one of the most widespread and common dragonflies there. The distribution ranges from California to the far north, so that C. resolutum is one of the dragonflies with the northernmost and therefore coldest habitat. The larvae, protected by anti-freeze substances in the blood, can be frozen in the ice for wintering. Are populated with sedges and horsetail covered swamps, ponds, and the edge regions of greater lakes. Coenagrion resolutum is with Coenagrion angulatum and Coenagrion interrogatum one of three species of azure virgin in America.
features
Characteristics of the adults
Coenagrion resolutum is a typical slender dragonfly with a body length of 27 to 33 millimeters and a length of the hind wings of 15 to 20 millimeters. The male adults have a blue base color on the upper side of the thorax and abdomen , which turns into a light green on the side surfaces. Males that are not yet fully developed may have a blue abdomen but a brownish thorax. The blue-green eyes are dark on top, so that they appear to be covered by a cap. The median stripe on the upper side of the thorax is wide, the lateral ante-humeral stripes, on the other hand, are relatively narrow and can sometimes appear to be perforated, the following humeral stripes are wider again. The blue sides of the thorax underneath are structured by two fine black lines starting from the base of the wing, as is typical of the azure maiden. The unmistakable abdominal drawing of the middle segments shows a black area extending over two and a half segments and two short, dark stripes near the thorax. The second segment has a black U-shaped drawing typical of azur maid, with a broad base and narrow arms. This is sometimes described as reminiscent of a demon's head. The segments three to five are half black, half blue, six and seven are mostly black. The eighth through tenth segments are blue, with black markings only on the top of the tenth and paired distal spots on the top of the ninth.
The division of the antehumeral stripes is more common in some populations than in others; further north of the range, the black markings of the individuals are more extensive and it is more likely that the ante-humeral stripes are broken.
The females are more powerfully built; the thoracic drawing corresponds to that of the male, but the rear edge of the prothorax is lined with a light strip. The females appear in two color morphs, a light pinkish-brownish heterochromic (colored like the females) and a bright greenish to blue-greenish androchromic (male-colored) form. The abdomen is completely blackened on top, with the exception of fine pale rings at the segment ends. On segments seven to nine, the distal rings are slightly wider and blue in both color morphs.
Similar species
Coenagrion resolutum stands out from other slender dragonflies in the same habitat due to the light green color of the thorax and the larger black parts on the abdomen. The U-shaped drawing of the second abdominal segment has different proportions than the otherwise identical drawing of Coenagrion interrogatum , which also always shows openwork ante-humeral strips and a different drawing of the abdominal side surfaces. Northern dark populations of Enallagma annexum and Enallagma boreale , may also have a U-shaped mark on the second segment, but are larger than C. resolutum , just like Enallagma anna , which has significantly longer abdominal appendages.
The females of the two other occurring azure virgin species have light areas on the abdominal segments, as well as the goblet virgins occurring in the same habitat show colored areas either on the middle or the rear segments. Some small species such as Enallagma minusculum , Enallagma laterale and Enallagma recurvatum resemble C. resolutum , but do not have a light-colored prothorax margin and have a protruding thorn in front of the ovule on the eighth abdominal segment. In addition, a color-contrasting, horizontal stripe in the middle of the eyes, which the azure maidens lack, is typical for the females of the cup maids.
distribution
The distribution of Coenagrion resolutum stretches from eastern Alaska across Canada to Iowa , Pennsylvania and Massachusetts . In the southwestern part of the distribution area, the occurrence in mountainous areas extends to Northern California and the central Rocky Mountains , where individuals have been detected at altitudes well over 3,000 m.
C. resolutum settled Seggensümpfe and well-covered ponds, as well as the Sedge large lakes and is often in herds of Pond horsetail found. In the southern part of the distribution area, shady, cooler habitats are preferred. The azure virgins are often associated with one of the two other species of the genus occurring in America, whereby in contrast to Coenagrion angulatum , which is more often found in sunlit waters, Coenagrion resolutum prefers at least partially shaded habitats.
Inventory and status
Coenagrion resolutum is one of the most common dragonflies in Canada and is native to many protected areas, including provincial and state parks in Canada and the United States. There does not seem to be any need for protective measures at the moment, the International Union for Conservation of Nature and Natural Resources (IUCN) resolutely classifies Coenagrion as “least concern”.
Way of life
Coenagrion resolutum can become very common in suitable habitats. The adults preferred to stay in the dense vegetation of grasses and sedges, so they are harder to find, as living in the same habitat enallagma ( Enallagma ). In the rest position, the wings are often slightly spread apart. As relatively weak fliers, they rarely - if at all - fly over open water, but can be found on peat moss mats. Mating begins away from the developing waters, for which purpose the males roam the vegetation in rapid flight in search of females ready to mate. The eggs are laid in flowing or upright plant stems, always above the water line.
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. However, compared to fast-growing species such as the pond damsel (Lestidae), the growth of the larvae is relatively slow and takes between 10 and 22 months. For wintering, the larvae, protected by anti-freeze substances in the blood, consciously seek out places where they can be frozen when the frost sets in. This behavior cannot be observed in the more southern, warmer parts of the range. The larvae remain in the diapause until the ice melts and then continue to develop. This leads to the formation of a hierarchy between the larvae, which aggressively defend favorable feeding places against other species. The newly hatched dragonflies leave the developing waters to feed and mature. Maturation to a sexually mature animal takes about a week. Under adverse circumstances, a semi-volatile development can also occur, in which C. resolutum needs two years to complete the development cycle.
The flight time of the adults differs with the distribution and ranges in Yukon and Ontario in northwestern and northeastern Canada from May to August, in the southern occurrences in Arizona and Ohio it is in June and July.
Systematics
Coenagrion resolutum is placed within the slender dragonflies in the genus of azure maidens ( Coenagrion ), which was created in 1890 by William Forsell Kirby . The genus, numbering 40 species, is mainly found in Europe and Asia and is only represented in America by Coenagrion angulatum and Coenagrion interrogatum in addition to C. resolutum . C. resolutum is more closely related to C. interrogatum 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.
Coenagrion resolutum was first described by Hermann August Hagen in 1876 , the specific epithet resolutum probably refers to the ability to cope with the requirements of a living space far north. The English name "Taiga Bluet" aptly describes the main distribution of the species in the North American taiga .
swell
literature
- John Acorn: Damselflies of Alberta, Flying Neon Toothpicks in the Grass. University of Texas Press, Austin 2011, ISBN 0-88864-419-1 .
- Robert DuBois: Dragonflies & Damselflies of the Rocky Mountains. Kollath + Stensaas Publishing, Duluth 2010, ISBN 978-0-9792006-8-7 .
- 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 e f John Acorn: Taiga Bluet. In Damselflies of Alberta , pp. 78-80.
- ↑ a b c d e f g h Dennis Paulson: Taiga Bluet. In Dragonflies and Damselflies of the East , pp. 84-85.
- ^ A b Dennis Paulson: Taiga Bluet. In Dragonflies and Damselflies of the West , pp. 75-76.
- ↑ a b c Robert DuBois: Taiga Bluet. In Dragonflies & Damselflies of the Rocky Mountains , pp. 98-99.
- ↑ a b B. C. Jones: Coenagrion resolutum on the website of the EH Strickland Entomological Museum of the University of Alberta . Retrieved April 15, 2013.
- ^ Coenagrion resolutum in the IUCN Red List of Threatened Species 2012.2. Listed by: DR Paulson, 2009. Retrieved April 3, 2013.
Web links
- Photos of "Coenagrion resolutum" - Taiga Bluet on odonata.bogfoot.net, with pictures