Boreal Bluet
Enallagma boreale, males
Enallagma boreale is a Kleinlibellenart from the family of dragonflies Slim ( Coenagrionidae ), which is common in large parts of Canada and North America and can be very common in northern latitudes. Be colonized ponds and marginal areas of larger lakes with high proportions exceptional out of the water vegetation. Enallagma boreale is a typical representative of the numerous group of blue-stained goblet Virgin and the other members confusingly similar, especially annexum of her in the ecological demands almost the same end Enallagma. The specific epithet is derived from Ancient Greek boreal βορέας boreas what " cold " means and at the same time refers to Boreas, the Greek god of the wintry north wind and was first described by Edmond de Selys - Longchamps chosen as an indication of the distribution area.
- 4.1 Literature
- 4.2 Notes and references
Features
Enallagma boreale is a typical Slim dragonfly with a body length from 28 to 36 millimeters and a length of hind wing 17-22 mm. The males have a bright blue color with large teardrop-shaped and also blue Postokularflecken on the body- facing side of the compound eyes. They are aligned with the top of another and connected together by a line. The eyes are dark upper side, so that they act as covered by a cap. The located on the top of the front body ( thorax) exploiting binding agents strip is conspicuously wide, whereas the lateral Humeralstreifen narrow. In the underlying light blue thorax sides there are two thorax side stripes, the upper is very rudimentary or no training, so that the side of the thorax surface appears as no drawing. The elongated abdomen is provided with a slender dragonflies typical drawing. The second segment bears at its lower end a large black umbrella- shaped cross bar, which can extend in some copies to the end of the segment. With representatives in the east of the range of that horizontal line is significantly greater. On the other segments three to five are each located at the caudal end of black rings, the widest on the fifth segment. The majority of segments six and seven is black, the eighth and ninth abdominal segment are quite blue, the tenth oberseits black again.
Northern populations, particularly in the highlands of Alaska and Canada have a far more extensive black markings, the Humeralstreifen are considerably wider, the Antehumeralstreifen can be broken. The drawing of the second abdominal segment acts as a great spot and touched the back edge of the segment. The drawing of the middle abdominal segments is increased, more than half of the fourth and fifth segment are blackened. Some populations have a prominent irregular black markings on the sides of the blue actually the eighth segment.
The abdomen of the female is stronger than that of the males built and stained oberseits predominantly dark, the abdominal segments each show only the front edge of the segments three to eight a bright ring. Before the ovipositor, on the eighth abdominal segment, there is a protruding spine. The bright staining of dragonfly is most pronounced on segment eight, this is sometimes even completely without black markings. The segments nine and ten are black. The eyes of the females are divided color horizontally, the upper part is dark, the lower Tan, on the lower part of the bright features usually still a dark horizontal band from. The thoracic figure corresponds to the males. How not uncommon in the subfamily Ischnurinae, the females come in various colors. There is a androchrome, as the males colored form, and a brown, straight chrome form.
Similar Species
A relatively young evolutionary splitting has led in North America to a large number of partially very similar and difficult distinguishable species. However, the cup Virgin companies are often formed only of a kind, and once determined, it can be assumed that all copies of this population only belong to this type. Preferences for various, at first glance very similar appearing, habitat types, they seem to separate, although these mechanisms are not yet fully understood.
Enallagma Enallagma boreale and annexum whose distribution areas overlap over a large area, form a pair of species that can not be distinguished in the field. Only by enlarging the study differing in fine detail male abdomen attachments are Enallagma Enallagma boreale and annexum, and also very similar Enallagma to distinguish vernale. Can annexum In E. Enlargement of the male abdomen attachments rearward lip- shaped elevation are found in E. boreale is this on the inside of Cerci.
Also very difficult to distinguish from boreal Enallagma Enallagma civile is, their distribution, however, overlaps with the boreal E. only to a small extent. E. civile has longer upper abdomen attachments as lower, exactly the reverse of E. boreale and Postokularflecken as well as, the rear end of the segment touching, drawing on top of the second abdominal segment are larger. Also hageni Enallagma Enallagma and Ebrium whose distribution areas coincide rather with that of Enallagma boreale, you resemble, but are smaller overall with smaller Postokularflecken and have larger spots on the second abdominal segment. The male abdomen attachments allow an unambiguous identification. In Enallagma clausum the drawing on the middle abdominal segments is usually less pronounced. With Enallagma carunculatum the distribution overlaps in some areas, but the males are easily distinguished by the extent of blackening of the middle abdominal segments and the different abdomen attachments.
The females of Enallagma Enallagma boreale and annexum are very similar, a determination may be made by comparing the prothorax and its typical shape of the trailing edge. This is constructed in E. annexum significantly while boreal E. merges with the thorax. In the females of other similar cup Virgin pronounced the bright eighth abdominal segment does not occur.
Dissemination
Enallagma boreale is widespread throughout western North America, the range extends from Alaska to the Mexican highlands of Durango, in the east it ranges from Labrador in the north to Iowa and West Virginia. Along the immediate Pacific coast E. boreale is less common than E. find annexum, generally more arid regions are preferred. In the south of its range primarily to higher altitudes are populated.
Way of life
Enallagma boreale can be very common in northern latitudes. Be colonized ponds and the fringes of large lakes with high proportions exceptional out of the water vegetation, including cold Tundratorfmoore. In the east, E. boreale is apparently limited to fish -free waters, not so in the West. The males are - typical of the cup Virgin - to be found in large numbers on the water, where they fly in high speed low over the open water and rest on Emersvegetation. Pairs are formed partly already far away from the water, frequently. Corridors of open forest areas Copulation takes on average 23 minutes, and then has a search for suitable oviposition sites on. Eggs are laid in tandem and can continue even under water. The average life expectancy of mature and reproductive imagines is four days with a maximum of 17 days.
The flight time differs with the distribution. In the Yukon it runs from May to July in British Columbia, however, from April to September. At the southern edge distribution in Arizona it lasts from June to October. In the north- eastern North America in Nova Scotia it runs from May to September and extends the southern range edge, in Ohio, to June.