Coenagrion mercuriale
Coenagrion mercuriale (Charpentier, 1840)
Local names: Southern damselfly, Helm-Azurjungfer, Mercuurwaterjuffer, Agrion de Mercure
Species Information
Description
One of the smaller Coenagrions. The males are light blue with black markings and bands on the abdomen. The characters for sure identification are small and should be observed carefully. The pterostigma is diamond-shaped (lozenge) and is blackish-brown with a lighter coloured border. The black marking on S2 is characteristic and resembles the helmet of Mercury, who according to roman mythology wore a winged helmet. The shape also looks like a U placed on a spearhead. It is always connected to the hind margin of S2. The females are green-blue with black markings. A correct identification of the females is difficult and can only be done with certainty by checking the shape of the pronotum.
Size
Habitat
Coenagrion mercuriale is found at unshaded, often calcareous runnels, small streams and irrigation ditches, preferably with a rich aquatic and riparian vegetation of Watercress and Fool's waterdress. The water is typically shallow and slow-flowing over a gravel or marl bed with patches of organic detrius. The vegetation near the banks often consists of low herbs and grasses and is frequently used for hay production or grazing. It is one of the few species that is mainly found in extensive agricultural areas. here it benefits from mowing of bank side vegetation and cleaning of waterways which prevents the habitat from becoming overgrown and shaded. In Great Britain the species is found runnels and streams in acidic heathland, chalk streams and calcareous fens. C. mercuriale is mostly found below 700 m in the middle latitudes, but can reach 1 500 m in the Iberian Peninsula (and over 2 100 m in Morocco).
Distribution
The main range of C. mercuriale covers France and the northern part of the Iberian Peninsula, where it is widespread and common. The species has a more scattered occurence in the southern half of spain and in Italy, where it is lacking north of the Po river. It is missing from all Mediterranean islands. In central Europe it is found in Germany and western Austria, where it is widespread but rare, with small local populations. In Belgium it is very rare, only found in two small areas in southern Wallonia. In the Netherlands it is considered extinct, although vagrants have been found. In Great Britain it is restricted to a small number of populations in Wales and the south and west of England.
Flight Period
April to August
Conservation Status
Similar Species
Coenagrion ornatum, Coenagrion puella
External Links
Genus: Coenagrion
Coenagrion is a genus of damselflies in the family Coenagrionidae, commonly called the Eurasian Bluets (although three species are found in North America). Species of Coenagrion are generally medium-sized, brightly coloured damselflies.
Identification
Males are small blue damselflies with black markings. The blue areas may be partly greenish or whitish. Females have more extensive black markings, and are more often green or brownish. A damselfly with plain pterostigmas, with roundish postocular spots, with antehumeral stripes narrower than the black line below it, and with two short black lines on the thorax sides, will in most cases belong to Coenagrion.
Separation from other genera
Enallagma normally have antehumeral stripes wider than the black line below them and just one short black line on the thorax side. Ischnura males have bi-coloured pterostigma. Enallagma and Ischnura females have a vulvar spine. Erythromma species are darker, with reduced or no postocular spots, and males have red or all-blue eyes, whereas eyes of Coenagrion are blue with dark caps. The blue Erythromma lindenii is very similar, but differs in many details, like wider antehumeral stripes, an all-black upperside to S2 and a shorter 'tail-light' positioned further at the tip of the abdomen.
Behaviour
Males typically fly low among or along riparian vegetation. They rarely venture far from water. MAles and females in tandems often oviposit in concentrations on floating vegetation. The male often holds a conspicuous upright posture when in tandem with the female.
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.