About Odonata
Dragonflies and Damselflies belong to the order of insects called Odonata. They all have two pairs of densely veined wings, and long, ten-segmented bodies which are often brightly coloured. Dragonflies are a very old order: fossils of dragonfly-like insects are known from Carboniferous rocks 350 million years old.
Odonata are divided into two suborders, Anisoptera (Dragonflies) and Zygoptera (Damselflies). There are about 5700 Odonata species known in the world today. Of the 52 species recorded in Britain, 38 have established breeding populations, one has dubious taxanomic validity, three formerly resident species have become extinct since 1950, and ten species are migrants, none of which has established a viable breeding population.
Dragonflies have a unique method of reproduction, with indirect insemination and delayed fertilization. Sperm is transfered by the male from the abdomen tip to the secondary genitalia at the abdomen base, from where it is passed on to the female. Eggs are not fertilised until they are laid, so males can remove sperm of rival males if they succeed in copulating with a mated female. This is why, in many species, the male protects the female while she is ovipositing.
Dragonflies have a three-stage life cycle. The egg hatches into the larva (also known as a nymph), which lives under water. The nymph moults up to 15 times before emerging as an adult. Unlike most other insects, there is no pupal stage and the transition from larva to adult is known as incomplete metamorphosis. This is not necessarily an annual cycle, since the nymph may spend more than a year underwater before emerging as an adult, and some species can complete the whole cycle in a few months. The adult stage is usually the shortest part of the life-cycle and rarely lasts for more than a week or two in Britain, although some species can live for much longer.
Both larvae and adults are predators. Both stages feed on other insects, but nymphs also take crustaceans, worms, snails, leeches, tadpoles and small fish.
Dragonflies and damselflies are suffering because of loss of or damage to their wetland habitats. Some species have very specific habitat requirements (for example seven species need acidic bogs and seepages), but others are less fussy and even a small pond can attract them.
Four species of dragonfly are regarded as being endangered in Britain, the Southern Damselfly, Northern Damselfly, Norfolk Hawker and White-faced Darter. A further two are vulnerable, the Azure Hawker and Brilliant Emerald, and a futher six species are near-threatened.