Common Blue Damselfly - Enallagma cyathigerum
Adult sizeOverall length: 29 - 36mm Hindwing length: 18 -20mm
Distinguishing featuresOne of the two most common of the five species of ‘blue’ damselflies found in Dorset. They have a characteristic ‘club’ or ‘mushroom’ shape on segment 2 of the abdomen. They tend to look more robust than the slighter Azure Damselfly, and will tend to fly out more in open water. It is very commonly distributed across UK and occurs in a wide variety of habitats
Identification - for help with terms see glossary
Mature males have a characteristic black ‘club’ or ‘mushroom’ shape on segment 2. They have thick blue complete antehumeral stripes. Also has solid blue markings on segments 8 & 9. From the side there is a just a single stripe on side of thorax, all other 'blue' damselflies having two stripes.
Are a pink/brown base colour which gradually turns blue. The eyes are brown at this stage, turning blue at full maturity.
Mature females like the Azure Damselfly occur in two forms; blue and green. On older green females the lower segments will eventually turn a dull brown colour. The black markings on the abdomen are very distinctively ‘rocket’ shaped, there is just a single stripe on the side of the thorax and females have a small spine underneath segment 8.
Immature females of the green form have with a pale base yellow colour which develops into the mature green colour. Blue from females begin like the blue males and will have a pale brown/pink base colour with brown eyes turning blue on maturity.
HabitatWill occur in almost any type of water body both still and running and can tolerate both nutrient poor and nutrient enriched conditions. Is often the most common species at larger open water sites such as lakes, reservoirs and large ponds. Often found with Azure Damselfly.
BehaviourMales can often be seen in high numbers males busily patrolling the water’s edge searching for females though they are not strictly territorial. Will tend to be more aggressive than Azure Damselflies. Immature stages will, like many species, be found away from water as they develop.
Status and distributionHas a very wide distribution found throughout Britain including Hebrides. One of commonest damselflies and found at virtually all suitable sites. Very common throughout Dorset.
Flight periodMain flight period is late April to Mid September, peaking in June, July & August.
Similar speciesVery similar to three other members of Coenagrion family occurring in Dorset, all of which could potentially share similar habitat; Azure Damselfly, Southern Damselfly and Variable Damselfly, though the latter two are very uncommon. Always look at segment 2 in the males for indentification. Special care must be taken with trying to identify females within this group.
More photographsClick on the photos below to enlarge...
All photographs by kind permission & © of Ken Dolbear unless otherwise stated. All rights reserved.