Dragonflies are large colourful insects usually found near fresh water such as riverbanks, canals, ditches, ponds and lakes. Their smaller relatives, the damselflies, are also found in similar habitats. Fossil evidence shows that they have been flying around for over 300 million years! In Britain there are 27 species of dragonfly and 16 species of damselfly. A total of 31 species have been recorded in Devon including many rarities. Dartmoor and its fringes, as well as the County’s heathlands, are particularly important for these creatures.
Most of a dragonfly’s lifecycle is spent underwater and it is only the short-lived adults that we normally see. Clean water is an essential requirement for dragonflies and damselflies and they are therefore good environmental indicators, their presence suggesting a healthy water environment. Being strong fliers many dragonflies can be found a long way from water, but all do require water to complete their life cycle.
Large male dragonflies can often be seen defending ‘their’ pond or stretch of canal bank by patrolling backwards and forwards and fighting off incomers. Mating is a somewhat unusual behaviour in this group of insects, with the male and female joining together by the male grasping the female behind the head with the tip of his abdomen. Sometimes the pair can be seen flying in this ‘tandem’ position.
After mating eggs are laid in the water or into the stem of an underwater plant. The nymph hatches out of the egg and takes 2-5 years to develop (depending on species). Whilst developing, the nymph is a veracious predator and when fully grown the larger species can tackle tadpoles and small fish. Once the nymph has fully developed, during late spring or summer, it crawls up a plant stem, splits its skin and the adult emerges. It takes a while before they can fly as their wings dry out and they pump themselves up.
Vegetation in the water is important for most species. Dragonflies and damselflies need roots to hide in as nymphs, not only for protection from predators, but also to hide from their prey when hunting. They also need to be able to get out of the water and have somewhere safe to change into their adult form. Vegetation (preferably native) also keeps the water cleaner and supplies it with essential oxygen.
Dragonflies and damselflies will travel long distances to find water, so building a pond (see Ponds and wetlands) can attract them fairly quickly, and if you’re lucky they might stick around. Of course, for the nymphs to survive the pond must have a good supply of food as well as established plants, so don’t be surprised if they don’t choose to lay eggs in your pond straight away – the likelihood is that the pond simply needs to mature a bit first. However, even relatively new ponds will provide a home for these beautiful creatures.
How to encourage dragonflies and damselflies
- Build a pond. Once established they will provide valuable habitat for dragonflies and much other wildlife.
- Ensure water bodies have a good mix of marginal vegetation as well as submerged plants. If necessary remove some excessive plant growth to leave areas of the water surface clear of plants.
- Avoid pesticides near water.
- If dragonflies insist on staying away from your pond, check to see if you have problems with water quality. Excessive nutrients from agricultural run-off cause algal blooms, and cloudy water from too much silt is caused by excessive soil or bank erosion. Dragonflies generally need clean, unpolluted water. See Ponds and wetlands.