Ischnura Elegans
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The blue-tailed damselfly or common bluetail (''Ischnura elegans'') is a damselfly, belonging to the family Coenagrionidae.


Subspecies and varieties

Subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...
and varieties include: *''Ischnura elegans ebneri'' Schmidt, 1938 *''Ischnura elegans elegans'' (Vander Linden, 1820) *''Ischnura elegans pontica'' Schmidt, 1939 *''Ischnura elegans f. infuscans'' *''Ischnura elegans f. infuscans-obsoleta'' *''Ischnura elegans f. rufescens'' *''Ischnura elegans f. typica'' *''Ischnura elegans f. violacea''


Distribution

This species is present in most of
Europe Europe is a continent located entirely in the Northern Hemisphere and mostly in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, the Mediterranean Sea to the south, and Asia to the east ...
and the Middle East. It is a common species.


Habitat

These damselflies can be found in a wide range of lowland environments, with standing and slow flowing waters, brackish and polluted water.


Description

''Ischnura elegans'' can reach a body length of and a
wingspan The wingspan (or just span) of a bird or an airplane is the distance from one wingtip to the opposite wingtip. For example, the Boeing 777–200 has a wingspan of , and a wandering albatross (''Diomedea exulans'') caught in 1965 had a wingsp ...
of about . Hindwings reach a length of .L. Watson and M. J. Dallwit
British Insects: the Odonata (Dragonflies and Damselflies
/ref> Adult male blue-tailed damselflies have a head and thorax patterned with blue and black. There is a bi-coloured pterostigma on the front wings. Eyes are blue. They have a largely black abdomen with very narrow pale markings where each segment joins the next. Segment eight, however, is entirely pale blue.BDS - British Dragonfly Society
/ref> At rest, the wings of most damselfly species are held back together, unlike dragonflies, which rest with their wings out flat. The thorax of juvenile males has a green tinge. Female blue-tailed Damselflies come in a variety of colour forms. Juveniles may be salmon pink, form ''rufescens''; violet, form ''violacea'' and a pale green form. The colour darkens as the damselfly ages. Mature females may be blue like the male, form ''typica''; olive green thorax and brown spot, form ''infuscans'' or pale brown thorax and brown spot, form ''infusca-obseleta''.


Biology and behavior

Adults fly from April to September to early October. The adult damselflies prey on small flying insects, caught using their legs like a basket to scoop the prey up while flying, or insects taken from leaves. Damselfly nymphs are aquatic, and prey on small aquatic insects or other aquatic larvae. A male can try to interfere with a mating pair, by attaching itself to the mating male. The females always lay their eggs on the floating parts of the plants without any involvement of the male. Blue-tailed Damselflies are superb fliers and can alter each of their four wings'
kinematics In physics, kinematics studies the geometrical aspects of motion of physical objects independent of forces that set them in motion. Constrained motion such as linked machine parts are also described as kinematics. Kinematics is concerned with s ...
in order to maneuver. A recent study has shown that they can compensate for a whole wing loss and even successfully maneuver and catch prey.


Female polymorphism

In damselfly populations, there is often a surplus of males displaying male mate harassment. In order to avoid unwanted mating attempts, females have developed polymorphisms that allow some of them to avoid recognition by males by mimicking male phenotypes. There are three specific morphs found in the ''Ischnura elegans'' species: androchromes, ''aurantiaca(rufescens)'' and ''infuscans.'' The androchromes resemble the male coloration, and the gynochromes, which can be either ''aurantiaca'' or ''infuscan,'' do not resemble males. The ''aurantiaca'' female morph is a pink-orange color with a blue abdominal patch that eventually disappears after maturation. The third morph, ''infuscan'', displays an olive-green coloration with no color on its abdominal patch. Females are able to fully mature into their differing morph colorations just a few days after they finish their transition from aquatic larvae to their mature forms. Although having an increased number of morphs makes it more difficult for males to distinguish between males from females, the levels of male mate harassment is different between the different morphs. Males primarily rely on visual cues to distinguish between the morphs and can also use odour cues, secondarily. Androchromes are often seen to face less male mate harassment because they resemble males and are less desired.  This gives androchromes an advantage in that they are able to spend more time allowing their eggs to mature instead of exerting energy avoiding unwanted mating attempts. Along with that, the morphs also display different mate avoidance tactics. Androchromes are more likely to face off with males by spreading their wings and curling their abdomens while gynochromes tend to fly away to avoid mating. Despite potentially having more time for egg maturation, the androchromes are still disadvantaged because their abdomens, like males, are more narrow which prevents them from being able to carry as many eggs as gynochromes. There are also five main hypotheses that attempt to understand how the different female polymorphisms are continually maintained in this species. The reproductive isolation hypothesis states that there is a greater predation pressure on androchromes, which is seen as a trade-off to maintain the more inconspicuous morph. The male-mimicry hypothesis, mentioned previously, proposes that the androchromes ability to mimic male coloration allows them to avoid unwanted mating attempts and allocate more time to egg maturation. The density-dependent hypothesis states that the maintenance of the polymorphisms is attributed to the changing population densities. The habituation hypothesis states that males are actually most attracted to the morph that is most abundant. Lastly, the neutral hypothesis proposes that the female morphs are maintained by
genetic drift Genetic drift, also known as random genetic drift, allelic drift or the Wright effect, is the change in the Allele frequency, frequency of an existing gene variant (allele) in a population due to random chance. Genetic drift may cause gene va ...
,
mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA or viral replication, ...
s, and founders effect all working together as well as that they might be more neutral to selection.


Mating and behavior

This species participates in a male scramble mate choice mating system in which a male's mating success is determined by how fast they are able to find a mate. This includes many hours of copulations in which males are unable to monopolize a single female and some males are often left with no mates at all. Due to this, the ''I. elegans'' species displays intense male-male competition which leads to males forcing copulations with females. Along with the lengthy copulations, the reproductive lifespan of this species is only a few weeks. Cooperation from both males and females is required for copulation and females have the ability to reject sperm transfer from unwanted mating attempts. A tandem formation is created by males through the clasping of the female pronotum. ''I. elegans'' have the ability to rapidly adapt to their environments which puts them under heavy selective pressures. As this species has originated from tropical environments, their hatching times are often shorter in warmer temperatures than cooler temperatures. Females are also more likely to spend time near bodies of water as that is where they lay their eggs. In response to changing social contexts and population densities, males may change their sexual preferences and choose to mate with other males.


Gallery

File:Blue-tailed damselflies (Ischnura elegans) mating, female typica 2.jpg, Mating, female f. ''typica'' File:Blue-tailed damselfly (Ischnura elegans) nymph.jpg, nymph File:Ischnura elegans emerging.jpg, emerging File:Blue-tailed damselfly (Ischnura elegans) immature male.jpg, Immature male Blue-tailed damselfly (Ischnura elegans) teneral female rufescens.jpg, teneral female form ''rufescens'' File:Blue-tailed damselfy (Ischnura elegans) female rufescens.jpg, Female form ''rufescens'' File:Blue-tailed damselfly (Ischnura elegans) female violacea 2.jpg, Female form ''violacea'' File: Blue-tailed damselfly (Ischnura elegans) female rufescens-obsoleta 2.jpg, Female form ''rufescens-obsoleta''


References


External links

* * {{Taxonbar, from=Q548472 Ischnura Damselflies of Europe Insects described in 1820 Taxa named by Pierre Léonard Vander Linden Articles containing video clips