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).
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 an imago). They become sexually mature in this final, adult stage.
In one order of insects, the mayflies (Ephemeroptera) there is also a sub-imago stage, just before the final adult stage. Nymphs of some orders of Exopterygota, including mayflies, live in water and crawl out of the water to achieve the land living sub-imago and adult stages.
The insect orders that undergo incomplete metamorphosis are:
- Biting and Sucking lice (Order: Phthiraptera)
- Booklice and Barklice (Order: Psocoptera)
- Cockroaches (Order: Blattodea)
- Dragonflies and Damselflies (Order: Odonata)
- Earwigs (Order: Dermaptera)
- Grasshoppers and Crickets (Order: Orthoptera)
- Praying Mantids (Order: Mantodea)
- Mayflies (Order: Ephemeroptera)
- Stick insects and Leaf insects (Order: Phasmatodea)
- Stoneflies (Order: Plecoptera)
- Termites (Previously Order: Isoptera but now part of Order: Blattodea)
- Thrips (Order: Thysanoptera)
- True Bugs (Order: Hemiptera)
- Web-spinners (Order: Embioptera)
- Zorapterans (Order: Zoraptera)
Back to Insect Orders.