Common blue damselfly (Enallagma cyathigerum)

French: Agrion Porte-Coupe, L’agrion Porte-coupe
KingdomAnimalia
PhylumArthropoda
ClassInsecta
OrderOdonata
FamilyCoenagriidae
GenusEnallagma
SizeWingspan: 38mm
Average body length: 32mm

The common blue damselfly is classified as Least Concern (LC) on the IUCN Red List (1). It is common in the UK.

As the name suggests, the common blue damselfly (Enallagma cyathigerum) is one of the commonest species in Great Britain. They can be confused with other blue damselflies and this situation isn't helped by the fact that the markings on this species are rather variable. Adult males are predominantly blue, spotted with black markings resembling stripes. Adult females are much darker with larger areas of black and usually a green background colour, although there is a blue form, again with larger areas of black.

Dragonflies and damselflies can appear alarming to some people, and their old English country names of ‘horse-stingers’ and ‘devil’s darning needles’ suggests they were once feared. This fear probably stems from the long and usually striped abdomen characteristic of these insects and the fact that they can curl their ‘tails’ down as if preparing to sting. In fact, neither dragonflies nor damselflies have the capacity to sting, although they are predatory insects, both in the larval and adult stages.

All flying insects evolved originally with two pairs of wings although, in some species, the front pair has become modified to act as wing covers. These species include various beetles, crickets and cockroaches. Other insects have effectively lost the hind pair of wings, having two pin-shaped balancing organs in their place. Dragonflies and damselflies have retained both pairs as membranous wings, both effective in flight. Both dragonflies and damselflies are strong and swift fliers, and both pairs of wings are similar in size. Apart from their smaller size and generally more slender build, the easiest way to distinguish damselflies from dragonflies is the position of the wings when the insect is resting. Dragonflies rest with both pairs of wings held perpendicular to the body, whereas damselflies hold them almost parallel.

Found across most of the UK, the common blue damselfly is probably the most widespread member of the ‘blue’ damselflies. It is also one of only two species of damselfly that can be found in both Europe and North America, its range almost completely circling the Northern Hemisphere.

The common blue damselfly is found around open lakes and ponds, along river and canal banks, and streams, provided there is plenty of bankside vegetation.

Common blue damselflies appear in mid to late May and their flight period lasts right through the summer months to September. Adults live for around 12 days on average and in this short period they must breed. Mating can take up to 20 minutes and the females lay their eggs in the tissue of plants both above and below the water line and are capable of remaining submerged for some time. The male will stay guarding her at the point where she entered the water.

Damselflies and dragonflies spend the greater part of their lives as larvae, sometimes as much as three years. The larvae are predatory hunters, feeding on other water creatures that also lurk amongst the waterweed. When ready to emerge, the larva climbs up a plant stem free of the water and, once the insect’s outer case has dried and split, the final perfect damselfly frees itself from the chrysalis by arching its body backwards. Once free, the adult insect pumps blood into its wing veins until the wings are fully expanded.

Common blue damselflies are still common and widespread and do not appear to be threatened. Provided they find clean water and plenty of marginal vegetation, they seem to be a successful species. They also colonise new water bodies, especially flooded gravel pits, extremely rapidly.

As the common blue damselfly remains widespread and common, there are currently not conservation plans for this species.

For more on British dragonflies:

Information supplied by English Nature.

http://www.english-nature.org.uk

  1.  IUCN Red List (April, 2011)
    http://www.iucnredlist.org/