Originally published 05/07/2015.
Today’s dragonfly has been chosen as it is the largest species of dragonfly we have here in the UK. The Emperor dragonfly, Anax imperator, can reach up to 84mm in length and with its vibrant colouration, it really is a treat to spot.
The Emperor dragonfly favours lakes and ponds that are well vegetated. They are also common along rivers, canals and large ditches. This species is very common in the south of England and Wales, getting slowly less common as you move up the UK mainland. It is found in northern England and Scotland but is less common in these areas.
The Emperor dragonfly is a very obvious species, with both sexes having an apple-green thorax. Both sexes have an irregular thick black line down the centre of their abdomen, along with a yellow costa and brown wing spots.
Male: abdomen is bright blue, except for segment one which is bright green. The male also has green-blue eyes.
Female: abdomen is a dull green or occasionally a dull blue. Eyes have a green tint.
Immatures: pale green, with a thick brown line down centre of abdomen.
Males are very territorial and will patrol regularly, flying very high up. They will aggressively chase away any intruding hawkers. Females are often difficult to see, sometimes they can be spotted whilst egg laying in water-side vegetation as their large wings will rustle amongst the vegetation. The Emperor often flies with its abdomen held curving downwards.
The Emperor dragonfly can reach speeds of up to 20 miles an hour, can fly very high and will travel large distances. As with all hawkers, it can be hard to differentiate between species whilst they are in flight due to their incredible speeds. However, if you get a close look, the Emperor stands out from other hawkers by the black line down the middle of its abdomen and by the apple-green thorax that is without black markings.
The Lesser Emperor, Anax parthenope, is very similar. It reaches lengths of up to 75mm so is slightly smaller than the Emperor, and it has a violet-brown thorax and a brown segment 1 which can help to tell it apart. It also has a yellow band across the bottom of segment 2.
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