Saturday, 13 June 2015

Azure,Variable,Red-eyed and Common-blue Damselfly ID Pointers.

The following is just a piece to compare females of the commonly encountered species of Azure,Common-blue,Red-eyed and the scarcer Variable Damselfly and some identification pointers in how to separate them in the field.I won't write lines and lines of text,but will let the photos speak for them selves.I have included Red-eyed Damselfly,as this is one i frequently get asked about 'What species is it' and it is similar in some respects when newly emerged as an immature.
Female Red-eyed Damselfly - Note robust build,with distinct dark topped thorax,green sides to thorax and short antehumeral stripes with ruby red eyes.When flushed it always gives the impression of being large and dark in flight.

Mature female Common-blue Damselfly - Note colour of abdomen when mature,but this species also comes in two colour forms.The key identification pointers are the broad antehumeral stripes along the top side of the thorax and lack of 'Spur' like marking found in Variable and Azure on the side of the thorax.It also shows the distinct bar between the post ocular spots when seen from above.If seen closely you will see the diagnostic spine under segment 8 of the abdomen which identifies this species from any other.

This individual is an immature female Common-blue Damselfly which has yet to colour up properly,but note the same features as the above photo.

Immature female Common-blue Damselfly - Showing thorax detail with the lack of 'Spur' as in Variable and Azure and the diagnostic,broad antehumerals as described above.

'Blue Form' Azure Damselfly - This can be confused with the similar female Variable Damselfly,but the diagnostic bar between the post ocular spots is not found on female Azure.If seen in the hand or at very close range,the pronotum shape is also a very good feature to separate the two species,with the pronotum on Variable being three pronged or 'Trilobite' in shape.Note the spur on the side of the thorax separating this species from Common-blue and also the brighter coloration of this species.

Female 'Blue' form Azure Damselfly showing the distinct 'Spur' marking on the side of the thorax and thin,slightly kinked antehumeral stripes when compared to Common-blue Damselfly.Please note that female Variable And Azure both occur in two colour forms Green and Blue.See my previous post about the identification of Azure and Variable Damselflies for some useful photos.

Female 'Blue' form Variable Damselfly - note the diagnostic shape of the pronotum and bar between the post ocular spots when compared to Azure which are both diagnostic features in seperating the two.This species should never be confused with Common-blue Damselfly.

Female 'Blue Form' Variable Damselfly - Note the male-like broken antehumeral stripes on this individual.Use the same features as the above photo to seperate Azure and this species.The bar between the post ocular spots isn't quite as prominent on this individual.

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