Ischnura elegans
Ischnura elegans (Vander Linden, 1820)
Local names: Blue-tailed damselfly, Common Bluetail, Große Pechlibelle, Lantaarntje, Agrion élégant, Större kustflickslända
Species Information
Description
One of the most familiar, widespread and abundant odonates in Europe, well-known from eutrophic habitats and garden ponds.
Ischnura elegans is a small damselfly with the dorsal part of the abdomen completely black except for S8 that is light blue. The immature males have the middle part of the abdomen bronze-brown in colour, while the head, thorax and a segment at the tip of the abdomen are light blue. Females appear in five colour forms: Immature females violacea have a lilac thorax. When maturing they become either very like the male, typica, or brownish or dull greenish, infuscans. Some females, rufescens, have a pink thorax at first, but become light brown with olive-green or brown S8, rufescens-obsoleta later. Old infuscans and rufescens-obsoleta may become very dark.
The eyes are dark on the upper part. The pterostigma of the fore wing of the mature male is bicoloured black and white, and is at least twice as long as wide. Immature pterostigmas are unicoloured whitish.
The tips of the male lower appendages diverge (viewed from above). The outer branches of the upper appendages (viewed from behind) are relatively thick and long; the inner branches are parallel to each other, but there is variation here. Males from southern Italy, Turkey, Crete, Cyprus and the Middle East, with crossed inner branches of the upper appendages, are known as ssp. ebneri. A narrow, upright projection on the hind border of the pronotum separates this species from all others, but is absent in some females and regionally in males from ssp. pontica, from the Hungarian Plain and northern Balkans to central Asia.
The taxonomy of this and related species is complex. South-western relatives have been split off as distinct species, but variation towards the south-east is less understood, with several subspecies named.
I. genei and I. saharensis remain relatively green on the head, thorax and abdomen base, but can only be separated in the hand, as can I. graelsii.
Size
Habitat
In large parts of Europe Ischnura elegans is the most common damselfly, being found in all kinds of standing and slow-flowing waters. It is very common on mesotrophic to eutrophic sites and is tolerant to rather high salinity and moderate acidity. The species is found from lowlands up to 1 600 m.
Distribution
Ischnura elegans occurs from western Europe to Japan. It is widespread and is one of the most common and abundant damselflies in Europe. Its range overalps with I. graelsii in parts of the Iberian Peninsula and the species is largely replaced by I. genei on the Tuscan archipelago, the Tyrrhenian islands and the Maltese Islands, although locally both species occur sympatrically and appear to produce hybrids.
Flight Period
April to October
Behavior
Males are territorial and mature individuals of both sexes stay close to the waters. Great numbers of individuals can be found in adjacent vegetation, near the shoreline or a nearby in higher grass.
Eggs are laid by females flying alone. Larval development is normally one year but in the northern parts of its range it is often two years. In good conditions it can be shorter, as short as 55 days between eggs being laid and imagos emerging have been observed in south-western Germany. Exuviae are found on straws out in the water or along the shoreline.
Conservation Status
Similar Species
Ischnura genei, Ischnura graelsii
External Links
Genus: Ischnura
Ischnura is a genus of damselflies known as forktails in the family Coenagrionidae. Forktails are distributed worldwide, including various oceanic islands. The males have a forked projection at the tip of the abdomen which gives the group their common name.
Identification
Small delicate damselflies. The males are easily recognised by their contrasting blue 'tail-light' marking at the end of the abdomen. The abdomen is otherwise largely black or bronze-black dorsally, with the underside of S3-S& yellow.
Males have a bicoloured pterostigma in the forewing. The inner part is dark grey while the outer part is whitish. At the base of the ovipositor the females usually have a small vulvar spine on the underside of S8.
Separation from other genera
The dark abdomen with blue 'tail-light' may recall dark-bodied Coenagrion or Erythromma species, but both these have unicoloured dark pterostigmas. In Coenagrion S2 is mainly blue, and dark Erythromma have conspicuous red eyes. The vulvar spine feature of the Ischnura is shared only with Enallagma females, however these differ in their abdominal markings.
Behaviour
Females of Ischnura oviposit alone, unlike other small damselflies who often do thisin tandem. After emergence, many adults remain close to water, often creating high proportions of mating pairs and tenerals at a site.
Family: Coenagrionidae
The insect family Coenagrionidae is placed in the order Odonata and the suborder Zygoptera. The Zygoptera are the damselflies, which although less known than the dragonflies, are no less common. More than 1,300 species are in this family, making it the largest damselfly family. The family Coenagrionidae has six subfamilies: Agriocnemidinae, Argiinae, Coenagrioninae, Ischnurinae, Leptobasinae, and Pseudagrioninae.
This family is referred to as the narrow-winged damselflies or the pond damselflies. The Coenagrionidae enjoy a worldwide distribution, and are among the most common of damselfly families. This family has the smallest of damselfly species. More than 110 genera of the family Coenagrionidae are currently accepted.
The family was named by William Forsell Kirby in 1890. The name may be derived from Greek coen meaning shared or common and agrio meaning fields or wild.