Dragonflies and damselflies made up the order Odonata. It is a relatively small group of insects with approximately 6,300 species known throughout the world.
Characteristics of dragonflies and damselflies
Odonates are insects of medium to large size,with bodies measuring between less than 2 cm and more than 15 cm. They are characterised by their swivel head with two big compound eyes, strong jaws and two pairs of membranous wingslarge and elongated.
Dragonflies (suborder Anisoptera) and damselflies (suborder Zygoptera) differ in the position of their eyes and the shape of their wings. Dragonflies have the eyes together or almost together and the base of its hind wings is wider. On the other hand, the damselflies have widely separated eyes and the base of its hind wings is as narrow as that of their forewings. In addition, dragonflies are usually stouter and rest with their wings outstretched, while damselflies are generally more slender and fold their wings over their abdomens when at rest.
Odonates are hemimetabolous insects, i.e. they go through an incomplete metamorphosis. Adults lay their eggs on aquatic plants or directly on water. From them emerge the nymphs,which live in the aquatic environment until their development is complete. When they have grown sufficiently, they leave the water and perform their final moult, transforming themselves into adults,which are terrestrial and flyers.
To breed, the adults return to the water bodies. During the copula,the male grabs the female by her neck or prothorax and the female connects her abdomen to the male's genitalia, forming a characteristic "wheel" or "heart shape".
Where do they live?
Odonates have their greatest diversity in the tropical forests, where they are favoured by the availability and variety of aquatic habitats, and climatic stability. They are also abundant in mountain areas,which offer different water bodies and climatic refuges in adverse conditions.
Nymphs inhabit fresh waters,generally calm and not very cold. The greatest abundance is found in ponds, lakes, rivers and streams with varied vegetation and warm temperatures. Some species specialise in springs, peat bogs or large rivers. Adults can move away from the water for hunting and may be found in meadows, forest clearings or along roads and roadsides.
What do they eat?
All odonate species are carnivores. The nymphs have a mouthpart, known as "mask", that they can quickly project to capture a prey. They feed on zooplankton, worms, leeches, insect larvae, snails, other odonates and even juvenile fish and tadpoles in the case of large nymphs.
Adults are extremely efficient predators, thanks to their excellent vision and manoeuvrability in flight. They consume as much prey as their own body mass daily and feed mainly on flying insects such as flies, mosquitoes, butterflies and other odonates.
Ecological importance
The primary ecological role of odonates is as predator and prey in the food chain. In the aquatic environment, nymphs help structure invertebrate and phytoplankton communities through their consumption of zooplankton. Adults help control insect populations in the terrestrial environment. In turn, nymphs are preyed by fish, and adults are preyed mainly by birds.
Finally, nymphs are very sensitive to environmental factors such as vegetation, temperature and water pollution, which makes odonates excellent bioindicators of the quality of freshwater habitats.
If you would like to know more about odonates or to identify the species that live in the Iberian Peninsula, please consult our bibliography on dragonflies and damselflies.
English 
Spanish