Dragonflies and damselflies can seem rather overwhelming to identify at first glance. They maybe bright and beautiful but they are fast and flighty.
There are several excellent guide books out there and I have used these and photographs to identify the species. This is great when you get a good look but often it is fleeting or you are unable to take a photo for later analysis, it also hinders swift recording in the field.
Flight characteristics and behaviour can be diagnostic, the size and patrolling nature of the Emperor dragonfly (Anax imperator) make it undeniable.
The brown body and amber wings make the Brown Hawker (Aeshna grandis) easy to spot, but the other Hawkers and Chasers are very similar.
It was the discovery of a new species on my patch - the Hairy Dragonfly (Brachytron pratense) that led me to consider the similarities between 4 species of dragonfly. The Hairy Dragonfly, Migrant Hawker (Aeshna mixta), Southern Hawker (Aeshna cyanea) and Common Hawker (Aeshna juncae).
All of these species except for the Common Hawker have been recorded on my patch and so I lack a suitable picture but I believe it is possible to identify these species just by observing their thorax, something that is more readily seen in flight through binoculars or fleeting glimpses when settled.
The markings on the side are very diagnostic for the Hairy Dragonfly and the Southern Hawker whilst the Migrant and Common Hawker are very similar, however if we also look at the top you can distinguish these two species.
The migrant lacks any marking to the top of its thorax whilst the others all have two parallel bars. These bars are not identical, Hairy Dragonflies are broad, the Southern Hawkers are more tapered on the top edge and the Common Hawkers bars are very thin and narrow.
The combination of the top and back of the thorax aid in ID and if you can make quick field notes it should help you identify these species more easily in the field.
If and when I get a good picture of a Common Hawker I will update the photos in this post.
