Once you have established whether you are looking at a dragonfly or damselfly certain anatomical features need to be observed to identify the species. These are introduced below along with the terms used to describe them. Ideally your identification will be based upon a number of these features. Colour is frequently used to assist identification, but ideally should not be used as the sole diagnostic feature as colour can change considerably with age and a number of environmental factors such as temperature.
Dragonfly
Male Southern Hawker Photograph © M. Randall
Damselfly
Male White-legged Damselfly Photograph © M. Randall
Head
Eyes
Frons
Photograph © M. Randall
Photograph © M. Randall
Photograph © B. Kemp
Eye colour can assist identification as well as the degree of contact between the eyes. The Golden-ringed dragonfly (above left) has striking green eyes clearly joining at a point. The Southern Hawker (above right) has a far broader contact point between the eyes.
The frons is the face area where colour and markings can aid identification. Above is a male White-faced Darter with a diagnostic white frons.
Thorax
Antehumeral stripes
Photograph © B. Kemp
Also referred to as shoulder stripes these can be diagnostic in terms of presence or absence, colour, thickness and whether the stripes are complete or broken. A female Broad-bodied Chaser is pictured above showing clear antehumeral stripes.
Side stripes
Photograph © S. Loose
Complete or partial stripes may be present or absent on the side of the thorax. Clear yellow side stripes are visible on the side of the thorax of this female Brown Hawker above.
Pronotum
Photograph © M. Justamond
The shape of the pronotum, in particular the hind margin is sometimes diagnostic in damselflies. An Azure Damselfly is pictured above with narrow antehumeral stripes and a wavy hind margin to the pronotum.
Abdomen
Segments
Photograph © M. Randall
10 segments are present numbered from the end nearest the thorax. When looking at a specimen it is easier to count the segments backwards starting at the end of the abdomen. Click on the Blue-tailed Damselfly above to get a closer view. Patterns and colour on the whole abdomen or on specific numbered segments may be diagnostic.
Shape
Photograph © B. Kemp
The overall shape of the abdomen can assist in separating male and female specimens and in identifying species. The abdomen may be parallel sided, waisted or noticeably club shaped as seen in the male Downy Emerald above.
Anal appendages
Photograph © B. Kemp
Anal appendages are situated at the end of the abdomen and can be diagnostic in shape and length relative to the abdomen. The Hairy Dragonfly above has distinctive long anal appendages.
Wings
Costa
Photograph © M. Randall
The costa is the vein on the leading edge of the wing and the colour of this can be diagnostic. The Emperor Dragonfly above has a clearly visible yellow costa.
Pterostigma
Photograph © B. Smith
The pterostigma is a thickened cell usually present toward the leading edge of each wing. It may be diagnostic in presence or absence, colour and shape. The female White-faced Darter above has dark coloured pterostigma.
Colour
Photograph © B. Kemp
Basal patches or bands of colour may be present on the wings as seen in the male Broad-bodied Chaser above. A suffusion of colour is also sometimes seen spreading through the wings as seen in the Brown Hawker (in the thorax section above).
Legs
Colour
Photograph © M. Randall
The overall leg colour or presence or absence of a stripe can be diagnostic. A Common Darter is pictured above with a yellow stripe visible on each black leg.
Shape
Photograph © B. Kemp
Leg shape can also be distinctive illustrated by the broader flattened legs of the White-legged Damselfly above.