Odonate of the week: Anax imperator

This week’s odonate of the week is a big girl…

Anax imperator female ovipositing

Anax imperator, the emperor dragonfly, is the largest (by weight) dragonfly in the UK. The golden-ringed dragonfly is marginally longer, but not as chunky. They can often be seen patrolling on larger ponds and lakes. Because of their size, they are powerful fliers. Like their North American counterpart, Anax junius, the green darner, they can make trans-Atlantic crossings (though mostly by chance rather than by intent).

In this photograph you can see a female ovipositing (laying eggs) into the stem of a water lily.  Odonates vary in where they lay their eggs, with some laying in open water, some on the surface of plants and some, like this emperor female, on the inside of plants.  The females of these latter species have sharp, pointed appendages called ovipositors through through which they lays eggs and they use these to cut open the plant stems to insert the eggs.  Other species also have ovipositors but they tend not to be as sharp.  These appendages can be used to inflict damage both on other odonates and on unwary entomologists…  They were thought to sting, hence the various folk names that they were given: “horse stinger”, “devil’s darning needle”, “troll’s spindle”.


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