Keeled Skimmer - Orthetrum coerulescens

Adult size

Overall length: 36 - 45mm   Hindwing length: 28 - 33mm

Distinguishing features

The smaller and thinner of the two skimmer dragonflies. Males have an all blue abdomen. Characteristically as with the Black-tailed Skimmer they will happily perch on open ground, rocks and logs and have a ‘hunched’ appearance as their wings tend to point forward.

Identification - for help with terms see glossary

Mature males

Male have power-blue pruinescence on a slender tapering abdomen with a thin line or keel running down the middle. They have blue eyes and the thorax is brownish with cream coloured antehumeral stripes though these can disappear with age. Wings look slightly tinted in appearance.

Immature males

May resemble female Blue-tailed Skimmer in that there are two sets of black like markings against a yellow base. Has a line through the middle and also cream antehumeral stripes lacking in Blue-tailed Skimmer. The blue pruinescence will develop with age.

Mature females

Females have a tapering ochre yellow abdomen with thin line or keel running down the middle and segments are well defined. Eyes are blue-green and the wings are suffused with yellow along the front of both wings. Females get darker with age and can become a dark olive green colour.

Immature females

Patterning is the same as adult but colour of eyes, thorax and abdomen is pale straw yellow which darkens with maturity.

Habitat

The Keeled Skimmer is closely associated with small rivers and streams in acid peat regions but may also be found in acidic standing waters such as mires, bogs and ponds.

Behaviour

Males will set up small territories along open banks where they will fly out often to inspect intruders, other males and other species returning to the same perch or patch. Like Black-tailed Skimmers they will characteristically bask in the open, often on exposed banks, stones or logs. Females can quite easily be found foraging on heathland away from water.

Status and distribution

Has a very patchy distribution reflecting is restriction to acidic conditions but found throughout the United Kingdom. Is a very common species on heathland sites in Dorset, less common elsewhere.



Flight period

Main flight period is May to September peaking in mid June to mid August.

Similar species

Males could be confused with Black-tailed Skimmer, and male Scarce Chaser but lack black tail markings and are smaller. Females are superficially similar to Common Darter females but these have two black markings on tip of abdomen and lack a definite keel.

More photographs

Click on the photos below to enlarge..

All photographs by kind permission & © of Ken Dolbear unless otherwise stated. All rights reserved.