The word Exopterygota refers to the development of the wings outside the body. Insects that develop in this way are said to show incomplete metamorphosis.
In the orders of insects which make up the Exopterygota, the larvae are usually called nymphs. After one or two moults, developing wings can start to be seen in sheaths on the outside of the nymphs.
Then there comes a time when they stop growing, moult again and become adults (also known as imagos). They become sexually mature in this final, adult stage.
Dragonfly nymphs are aquatic and must climb out of the water in order to moult in to the final, more familiar, adult form. The wing buds are clearly visible as two flat structures on the back of this dragonfly exuviae (moulted skin).
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