Species of the day: Emperor Dragonfly

James Duncan
, 10 June 2020
Species of the day: Emperor Dragonfly
Emperor Dragonfly - male © Neil Fletcher

By James Duncan

Learning and Engagement Officer

The impressive Emperor Dragonfly (Anax imperator) is rather appropriately named, for its bulky stature places it firmly in top spot as the largest British Dragonfly. Its naming seems doubly appropriate when witnessing the imperial nature with which this feisty insect goes about its business. It really is big, with the largest individuals topping out at over 8cm, a figure that gives it a legitimate claim for the title of 'UK's largest insect.' The wingspan is even longer, though its lightweight frame denies it top prize in the weight category, bested by some terrestrial insects. Not only are they big, they're fast and have magnificent stamina. This may see them reaching speeds of over 20mph, flying higher and further than the majority of other species and patrolling their territories almost endlessly. The Emperor belongs to a family of medium-large dragonflies, Aeshnidae, loosely known as the 'Hawkers', who all hunt and pursue prey in flight. Both sexes are particularly distinctive, displaying an apple-green thorax and long black line running the length of the abdomen, which is blue in the male, green in the female.

Though the mighty Emperor is large, it would have been dwarfed by some of its ancient ancestors, who prowled the oxygen-rich Carboniferous skies 300 million years ago. By the end of the Permian, around 250 million years back, some of today's familiar taxonomic dragonfly families were already beginning to be formed. This extraordinary lineage marks the dragonflies (Anisoptera) as perhaps the most remarkable winged wonders on the planet. Their evolution has enabled sensational feats of aerial agility, huge flight muscles within the thorax directly connected to their beating wings. As the thorax is quite simply a powerhouse of locomotion, the interior of the exoskeleton is heavily strengthened to withstand the huge forces generated. It's a rather wonderful morphological feature as each wing is carefully controlled by a separate muscle. This results in exquisite flight control, an ability to twist the wings on both upstroke and downstroke providing immediate lift and flawless control. The power generated creates vortexes of 'unsteady airflow' which sound disastrous, but may in fact pave the way for the development of future aircraft. Their mastery of the air has already inspired advances in drone technology and space exploration. 

The male Emperor has a supremely territorial nature. He won't just chase away intruders, he'll viciously clash with other Dragonflies in bouts of aerial supremacy. The rasping sounds of their chitinous wings colliding may travel a surprising distance and now is a marvellous time to start observing these titanic battles, typically over larger well-vegetated waterbodies. When not on 'fighter patrol' the Emperor will be chasing down a variety of insects, using its well-positioned legs to catch and hold them up to its mandibles whilst it feasts. It'll rarely alight, though a taste for large butterflies and even other dragonflies means it may have little choice but to stop and eat on occasion. Though an adult Emperor may live for a couple of months or more, it'll spend around ten times longer living underwater as an aggressive predatory larvae. These are as voracious as the adults and will gorge on anything smaller than themselves, including tadpoles and small fish, caught using well-developed eyesight, powerful jaws and an incredible form of underwater 'jet propulsion.' As they spend such a significant time living aquatically, the ongoing conservation of our waterways is key to their continued success. The creation of new wetland habitat, cleaning-up of rivers and warming climate have all contributed to the northward march of the Emperor as it continues to colonise new areas. 


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Comments

  • Daniel Ironside:

    Fantastic creatures and thanks for the informative write up. I think we may have seen some of these recently near lake wood? If you have any suggestions where else they may be lurking I’d love to know! Thanks.

    17 Jun 2020 19:54:00

  • Wendy Williams:

    I had one of these in my conservatory to day. I lifted him out with a bird scoop.

    03 Jul 2021 21:31:00

  • C Raeburn:

    One landed on my shoulder in York – they are huge!

    04 Aug 2021 09:24:00

  • Tony murray:

    Hi I seen some of these beautiful insects at Cape Cornwall, on the coast.

    16 Jun 2022 00:04:00

  • Colin Newman:

    I have two emperor dragonflies just emerging from their time living and feeding in my pond. Great to see as I only dug and filled my wildlife pond last June.

    26 Jun 2024 20:01:00

  • Colin Newman:

    I have two emperor dragonflies just emerging from their time living and feeding in my pond. Great to see as I only dug and filled my wildlife pond last June.

    28 Jun 2024 18:43:00

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