Enallagma carunculatum

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Enallagma carunculatum
Mating wheel of Enallagma carunculatum

Mating wheel of Enallagma carunculatum

Systematics
Subordination : Dragonfly (Zygoptera)
Superfamily : Coenagrionoidea
Family : Dragonfly (Coenagrionidae)
Subfamily : Ischnurinae
Genre : Cup maid ( Enallagma )
Type : Enallagma carunculatum
Scientific name
Enallagma carunculatum
( Morse , 1895)

Tule Bluet is a dragonfly from the family of Coenagrionidae (Coenagrionidae). It is native to North America.

features

Enallagma carunculatum reaches a body length of 27 to 37 millimeters. The males are colored light blue and black, in general the male has more black parts than light blue, the spots are triangular. The black banding becomes wider from segment to segment towards the rear end. There is a color polymorphism in females . There are androchrome, that is, females colored light blue like the males, but they can also be light gray, green and black. The first three abdominal segments are darker than in other species of the genus Enallagma , the eighth segment is pale at the base.

It is still not clear why there are several color morphs in females and none of these morphs over the evolution selected was. Studies on Enallagma carunculatum have shown that the light blue color variant reflects much more UV light than the green females. However, these have other distinguishing features, above all the color pattern and color saturation, which signal the males their presence. Scientists have often assumed that the light blue color morph has established itself as an imitation of the appearance of males. However, this is unlikely because the distribution of black proportions in females is very different from that in males. These therefore rarely fly to other males, but very often the light blue females that reflect the UV light. The different variants are more a question of competition between females who address different areas of perception of the males. Only to the human eye do the males and the androchrome females often look confusingly similar in the field.

Occurrence

The species is widespread in North America and is mainly found in the USA and Canada . In the southern parts of Canada, they range from Nova Scotia in the east to British Columbia in the west. In the north of the United States it is also at home from the east to the west coast, its range extends south to Maryland , Oklahoma , New Mexico and the Mexican state of Baja California . It is not found in the southeastern United States, where other species of the Enallagma genus are represented.

Enallagma carunculatum lives on rivers, lakes, ponds, swamps, moors, especially where there is a lot of reed . In the USA it is called Tule Bluet , after the pond rush called Tule (pronunciation: ˈtuːliː ) in America .

Way of life

The adults hunt many flying insects , including mayflies , two-winged birds , small moths , sometimes even smaller insects such as aphids , etc. The larvae feed on insect larvae, sometimes from the larvae of the animals that live in the same body of water, which also serve to feed the adult dragonflies .

The flight time is slightly different depending on the latitude . It begins in mid-May at the earliest and in early July at the latest and then lasts until mid-September or mid-October. The males occupy a territory that they have chosen as suitable for brood. then they fly to a female, usually around noon or in the early afternoon, and clasp it with abdominal forceps. Then the two dragonflies form a pairing wheel . The male's grip on the female remains even after mating, until the two of them together reach a reed in tandem, in which the eggs can be laid by the female.

Phylogeography

38 species from the genus Enallagma live in North America, while only four species are distributed in the Palearctic . The phylogeographic spread and differentiation of new species took place during the Quaternary Ice Age . The retreat of the glaciers and new advances of the ice were the reasons for the development of separate distribution areas in which separate groups of species emerged. A group of 17 species has its greatest biodiversity in the United States' New England states , between Connecticut and Maine , where the ice began to retreat around 15,000 years ago. It is believed that this area was also the starting point for the diversification of a group of seven species, all of which are very closely related to Enallagma carunculatum . In addition to Enallagma carunculatum , this group also includes E. anna , E. aspersum , E. civile , E. doubledayi , E. geminatum and E. praevarum .

literature

  • Albert Pitts Morse: New North American Odonata. Psyche, A Journal of Entomology, 7, pp. 207–211 and pp. 274–275, Cambridge, Massachusetts 1895 (first description)
  • JG Needham and MJ Westfall: Dragonflies of North America. University of California Press, Berkeley 1955

Individual evidence

  1. ↑ Gerrit Joop: Maintenance of female color polymorphism in the coenagrionid damselfly Coenagrion puella. Department of Biosciences and Psychology at the Technical University Carolo-Wilhelmina, Braunschweig 2005 Online (PDF, engl.)
  2. ↑ Stephanie Hatchew, GaHee Kim, Vanessa Sheu: The effects of UV reflectance on mate searching in Enallagma carunculatum. University of Michigan Biological Station, 2007 Online (PDF; 148 kB)
  3. ↑ C. Johnson: Polymorphism and natural selection in Ischnuran damselflies. Evolutionary Theory, 1, pp. 81-90, 1975
  4. ↑ TN Sherratt: The evolution of female-limited polymorphisms in damselflies: a signal detection model. Ecology Letters, 4, pp. 22-29, 2001
  5. ↑ Julie Turgeon, Robby Stoks, Ryan A. Thum, Jonathan M. Brown, and Mark A. McPeek: Simultaneous Quaternary Radiations of Three Damselfly Clades across the Holarctic. The American Naturalist, 165, 4, pp. 78-107, 2005

Web links

Commons : Enallagma carunculatum  - album with pictures, videos and audio files