Dragonflies and damselflies are very common insects – 25 species of dragonfly and 13 species of damselfly are found in the southwest of Western Australia. They are also very ancient insects. Fossils of damselflies have been found that date back to the Permian Period (280 – 225 million years ago).
Both belong to the same order of insects but are in different suborders. The main differences are:
- Dragonflies, in general, are much larger in size than damselflies.
- Dragonflies hold their wings out to the side (like an aeroplane) when at rest while damselflies hold theirs behind them.
- Larval damselflies have external gills while larval dragonflies have internal gills.
Dragonflies and damselflies lay their eggs in water and the larvae are aquatic. That is why the adults are usually found near water. It is only when the adult is about to emerge that the larvae leave their watery home.
Some species in cool climates can remain as larvae for 10 years or longer. The speed of development depends on the temperature of the water – warmer water quickens development. Whereas opportunistic species, that breed in temporary pools, can conclude a generation in as little as eight weeks.
Both the larvae and adults of dragonflies and damselflies are carnivorous and eat other insects. The adults can sometimes be seen chasing a moth or midge through the air before perching on a twig to devour it.