Enallagma annexum

Enallagma annexum 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. Are populated marshy open lakes and ponds, often bog lakes. Enallagma annexum is a typical representative of the numerous group of blue-stained goblet Virgin and the other members confusingly similar, especially in their ecological requirements, nearly the same end Enallagma boreale. Only recently it was recognized that the population of Nearctic Enallagma annexum, as Common Blue Damselfly previously ( Enallagma cyathigerum ) was identified, although this is very similar, but is genetically separated from her. It has since been as Enallagma annexum. The first description of the species in 1861 by Hermann August Hagen.

  • 4.1 Literature
  • 4.2 Notes and references

Features

Enallagma annexum is a typical Slim dragonfly with a body length from 29 to 40 millimeters and a length of hind wing 18-20 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 on top of the front body ( thorax) placed center 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 a wide black, often crescent- shaped, curved, horizontal line at its lower end. On the other segments three to seven are located caudally located, widening black rings, so that the segments six and seven look almost completely black. The eighth and ninth abdominal segment are then completely blue, the tenth oberseits black again.

The populations in Alaska and Canada west of the Rocky Mountains appear darker because of more extensive black drawing. Your Humeralstreifen are wider and the black markings of the abdomen is much more pronounced. On the second abdominal segment there is an extended spot, a large part of the abdominal segments four and five is black. The populations on the Pacific coast are darker than the average of the interior.

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 annexum is indistinguishable vernale of Enallagma without magnification examination of the differing only in fine detail male abdomen attachments. In E. vernale each Cercus has a knob-like thickening at its distal end, at the foot of which a small black tooth is next to a small recess. E. annexum lack these features, there appear, however, either by natural variation or by hybridization, repeatedly intermediate types that share characteristics of both species. E. vernale found relatively frequently in waters with fish, E. annexum seems to avoid this, or here can not reproduce.

Also very difficult to distinguish annexum of Enallagma Enallagma boreale is. In the former, a rearward lip-shaped survey can be found in the enlargement of the male abdomen attachments in E. boreale is this on the inside of Cerci. Enallagma Enallagma civile annexum also very similar, but this type has a longer upper abdomen attachments as lower, exactly the reverse annexum to E.. In E. civile also the drawing on the top of the second abdominal segment is larger and touched the rear end of the segment, this indicator separates E. civile of E. annexum and E. boreale in areas in which overlap the distribution areas of these dragonflies. Annexum Also of Enallagma very difficult to distinguish Enallagma clausum, in this drawing on the fifth abdominal segment is usually less pronounced. Enallagma Also hageni and Enallagma Enallagma annexum Ebrium resemble, but are generally smaller and have smaller Postokularflecken, this may be particularly in the determination of the females of concern. In most areas in which the distribution areas of dragonflies overlap, distinguishes the cross mark on the second abdominal segment E. annexum of the two smaller species that have larger spots here.

The females of Enallagma annexum, Enallagma Enallagma boreale clausum and are very similar, a determination can 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. Corresponds to the shape of the prothorax of E. clausum rather the annexum of E., but the anterior margin is constricted and on the top there are two small pits. In females of Enallagma recurvatum the eighth abdominal segment is also almost entirely without drawing, but these are much smaller. In the females of other similar cup Virgin pronounced this bright eighth abdominal segment does not occur.

Dissemination

Enallagma annexum is widespread throughout western North America, from Alaska to northern Baja California, in eastern North America from Newfoundland to West Virginia.

Way of life

Annexum Enallagma can be very common in northern latitudes. Are populated marshy open lakes and ponds, often bog lakes. In eastern North America it is a typical dragonfly fish-free waters. In the West E. annexum also slowly flowing rivers to be found and not tied to fish -free waters in California even just flows are probably settled.

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 or resting on the edge of dense vegetation structures. Mating usually takes place on sunny clearings close to the water, where copulation takes 10 to 27 minutes. Eggs are laid in floating and not protruding from the water vegetation, while vascular plants are preferred against algae. Previously, many potential nesting sites are checked. Eggs are laid usually in tandem, possibly the couple and the female separates dive headfirst off to continue this under water, it can dive time be up to 90 minutes. Usually the male guards his mate on the water surface, there is often after some time. It comes to hybridization with Enallagma vernale.

The flight time of the Imagines differs with the distribution. In the Yukon it is from June to August, in California, however, it lasts from April to November. In eastern North America, it starts in May and extends the southern range edge, in Ohio, to July, on the northern edge, in Nova Scotia, until October.

Swell

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