The mighty Emperor

In dragonflies, males are generally classed as fliers or perchers. Fliers spend most of their time on the wing – and have longer wings – whereas perchers spend most of the time sitting on a perch, from which they make short flights, defending territories and seeking females. The emperor dragonfly, Anax imperator Leach (Aeshnidae) is a typical flier, often patrolling the perimeter of a large pond on which they have established their territory, or ‘beat’, usually over one particular part. They are much easier to photograph however, when they are warming up in the sunshine at the end of the day: basking (below).

Emperor Dragonfly (Anax imperator) female, Beds, UK/ Raymond JC Cannon

The emperor dragonfly (or Blue emperor to give it its full name as there are 32 species of Anax worldwide!) has a huge distribution; from South Africa, through to northern Europe and into much of south-western and central Asia. It is also the largest dragonfly in western Europe. The larvae usually take about two years to develop.

Anax imperator larva, The Netherlands. This image is created by user Wim Rubers at waarneming.nl, a source of nature observations in the Netherlands., CC BY 3.0 https://creativecommons.org/licenses/by/3.0, via Wikimedia Commons.

The adults usually emerge in the Spring, from mid-May to early June, and the males tend to emerge earlier than females. Newly emerged adults are early risers, and fly shortly before sunrise. On the maiden flight they fly away from water, up to several hundred metres before alighting. They stay away from water for about two weeks or so, as they mature sexually, and during this period show no sexual interest in other dragonflies.

Emperor Dragonfly (Anax imperator) male Beds, UK. Raymond JC Cannon

The cerci, or appendages at the end of the abdomen, are rather different in males and females (below).

The males start to show interest in females after about 9-10 days of adult life, and copulation occurs as soon as a female arrives at the male’s territory. Oviposition follows (below), and both sexes return to the water frequently after the first mating.

Anax imperator, female, depositing eggs. Ocrdu, CC BY-SA 4.0 https://creativecommons.org/licenses/by-sa/4.0, via Wikimedia Commons

The males fight and considerable mortality can result from damage sustained by clashes with other dragonflies over their territories. Apparently, these clashes occur as a male tries to grasp a female and also fights with other males. Competing males can even bite each other, causing considerable damage, and such mid-air fights occur regularly in males of A. imperator. I have not yet managed to photograph one in flight, as shown below.

Emperor Dragonfly in flight, Flickr CC Tom Lee. https://www.flickr.com/photos/68942208@N02/27869558474/

Scientists have fitted small radio-tracking devices (weighing 0.29g) to Emperor dragonflies. One individual travelled more than 5 km over a period of 10 days (Levett & Walls, 2011). Females have larger home ranges (about 50 ha) than males (about 5 ha), because males tend to stay around their territories (Minot et al., 2021).

High trees are the preferred place to rest when air temperatures are low, especially for females, and emperors can often be seen basking in the late afternoon, catching the last rays of the sun before it sets. I took this photograph (below) in Spain.

Emperor dragonfly, Anax imperator basking in the late afternoon sunshine. Galicia, Spain. Raymond JC Cannon.

These are magnificent insects are widespread and common in Britain, and with climate change they are starting to move north into Scotland.

References

Corbet, P. S. (1957). The life-history of the emperor dragonfly Anax imperator Leach (Odonata: Aeshnidae). The Journal of Animal Ecology, 1-69.

Corbet, P. S., & May, M. L. (2008). Fliers and perchers among Odonata: dichotomy or multidimensional continuum? A provisional reappraisal. International Journal of Odonatology11(2), 155-171.

Levett, S., & Walls, S. (2011). Tracking the elusive life of the Emperor Dragonfly Anax imperator Leach. J Br Dragonfly Soc27, 59-68.

Minot, M., Besnard, A., & Husté, A. (2021). Habitat use and movements of a large dragonfly (Odonata: Anax imperator) in a pond network. Freshwater Biology66(2), 241-255.

2 thoughts on “The mighty Emperor

  1. Pingback: The Mighty Emperor – Cheshire Dragonflies Website/blog

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