Dragonflies form an important part of Wetland wildlife and they play a significant roll in its general ecology. They are among the most beautiful and spectacular insects flying today and they are also among the most ancient of living creatures.

2. Their life history

Metamorphosis. This is another word for transformation and, in the insect world, it is applied to the changes that take place during the lifetime of a single individual. During the development of some insects there is virtually no change in form (except for size) from the moment of hatching out of the egg, to the fully mature adult. For instance, a newly hatched cricket larva is, in appearance, a tiny wingless replica of its parent.

At the other extreme, there are species that enjoy a complete metamorphosis: in the Order Lepidoptera (butterflies & moths), for example, the egg hatches into the caterpillar (larva) which pupates into the chrysalis (pupa), from which emerges the adult (imago).

Between these two forms of insect development is that of those subject to partial change and it is here that we find odonates. The pupal stage is omitted but the differences between larva and imago are considerable.

The Egg. Odonates have two different methods of laying eggs and the basic shape of the egg depends on the method used. All damselflies and, among dragonflies, the members of Aeshnidae (Hawkers), Neopetaliidae (Redspots) and Petaluridae (Petaltails) are endophytic which means that, having well formed ovipositors, they insert their eggs into plant material above or below the surface of the water; this is the more primitive method. Most other dragonflies are exophytic: these lack functional ovipositors and merely deposit their eggs directly onto the surface of the water or into mud at the water's edge. The eggs of endophytic species are long and cylindrical, while those of exophytic species are broad and elliptical.

At one end of the egg there is a minute hole through which the sperm enters just before oviposition and from which the larva will later hatch. In some species the eggs are surrounded by a jelly-like substance that enables the eggs to attach themselves to the leaves of plants or to stones and rocks under the water, so preventing them from sinking into the mud or being swept away by fast-flowing water. Although some species over-winter as eggs, most eggs start to develop soon after they have been laid and the larvae hatch out one to three weeks later.

The Larva. This is the growth stage of an insect's life. Like all Arthropods, the developing larva must repeatedly shed one outer casing in order to grow a new one. Periods between these moults are called 'instars' and the number of instars necessary to complete development varies between eight and fifteen. By the time the aquatic larva reaches its final instar, it will have developed all the organs and other attributes that will be needed to sustain life as a winged terrestrial insect.

Odonate larvae are aquatic and breathe through gills. In most damselflies, these take the form of three leaf-like appendages at the tip of the abdomen, whilst the gills of dragonflies are projections within the rectum. Both respiratory systems also serve the larvae as means of moving around in the water: damselflies' appendages are used as rear paddles and the pump that ventilates the dragonflies' rectal gills provides a spectacular jet propulsion.

The larvae of dragonflies have robust bodies that are somewhat bullet-shaped if they live amongst water plants, or flattened if they live in bottom deposits. Damselfly larvae have slender, cylindrical bodies ending in the three conspicuous leaf-like gills which sometimes bear striking patterns. Their chief predators are fish and frogs while their main source of food is fish-spawn, tadpoles and the larvae of smaller insects. The larval stage can vary in duration from about three months to four or more years.

Emergence. The larva having completed its growth and development will, when circumstances are right, leave its aquatic environment and start a new life, almost completely divorced from water. Although some species of odonates can emerge on a flat surface (Gomphidae for example and most damselflies), the majority need a vertical one; the larva climbs up the stem of a reed or other plant, until it is well out of the water, and affixes itself firmly by means of its claws. After a pause, the larval casing breaks at the back of the head and, slowly and laboriously, the adult insect emerges. 'Blood' is then pumped strenuously round the body, an action that expands the body and also the wing-buds, transforming them into the beautiful lace-like wings which the insect will soon use to fly away from the water.

The Imago (adult). The necessary growth having been achieved during the larval stage, the imago can concentrate on ensuring the continued existence of its species: it is the stage of dispersal and reproduction.

(i) Dispersal period.
Immediately after emerging, young adults instinctively head away from water and fly off into the surrounding countryside. The dispersal period, which lasts from a few days to two or three weeks, is important in two ways. First, as will be seen later on, it has probably accounted for the survival of the Order Odonata. Secondly, it is the period during which the newly emerged insects attain full coloration and sexual maturity: they will not make their way to water until they are ready to mate..

(ii) Reproductory period.
This period lasts around two to three weeks in dragonflies and one to two weeks in damselflies, although the period is sometimes considerably extended.

The mating of odonates is virtually unique in the animal kingdom: although his sperm is produced (as is normal in all insects) near the tip of his abdomen, the male has an accessory organ on the underside of his second abdominal segment to which, prior to mating, he must transfer his sperm. When a male encounters a receptive female he will use the appendages at the extreme tip of his abdomen to clasp her securely behind her head (dragonflies) or neck region (damselflies) and both partners will curve their abdomens so that the female's genitalia engages with the male's accessory organ, the pair thus forming the characteristic 'wheel' position. Depending on species, mating may last from a few seconds to more than an hour. Before actually ejecting his own sperm, the male will sometimes remove any that may have been deposited by a previous suitor. Promptly after mating, the female will commence egg-laying and will then fly away from the water until she has another batch of eggs ready for fertilisation.

(iii) Egg-laying.
In some species this is carried out in tandem, the male continuing to hold his mate's head or neck while she deposits her eggs. In other species, the pair separates but the male will hover over the female, thus discouraging other males from mating with her. In a third group, the female oviposits totally unattended but, in these cases, she will do so in secluded places, often under a bank or among thick vegetation.

(i) During their lifetime, odonates experience two totally different lifestyles. In almost all cases, the oval and larval stages are spent in water whilst the adult stage is an aerial one. Following emergence from their larval casing, the newly-winged insects instinctively fly away from the water, dispersing into the neighbouring countryside and sometimes travelling very considerable distances. This dispersal period has been a vital factor in their survival. Over the millennia, should one piece of water have dried up or should a river have changed its course, odonates were able to find suitable alternatives and would quickly colonise them. (Sadly this is no longer the case and it has become urgent that steps are taken to halt the decline in the number of suitable breeding places.)

Dragonflies are among the most ancient of living creatures. Fossil records, clearly recognisable as the forefathers of our present day odonates, go back to Carboniferous times which means that the insects were flying more than 300 million years ago, predating dinosaurs by over 100 million years and birds by some 150 million. It would be tragic if, after surviving such an unimaginable number of years, it should be our generation that witnesses a serious decline of these fascinating and beautiful insects.

Odonates develop in water and, in order to protect them, it is necessary to study the exact habitat requirements of each individual species and then to protect, conserve and, where possible, increase the number of suitable habitats. The habitat requirements of some species are narrow and these are obviously the ones that are most at risk. Other species species are catholic in their needs and will survive in almost any kind of water, a few even tolerating water that is brackish. The majority fall between these extremes, some requiring running water, some still and some bogs and marshes.

Sadly, suitable sites are disappearing faster that new ones are formed and, until that trend is reversed, there is continuing cause for concern. Rivers become polluted; ponds are allowed to become clogged up with debris and week; marshland is drained to satisfy the ever increasing demand for roads and houses; primeval forests are disappearing and, with them, the mountain streams which contain some of the world's most interesting and primitive species.

Important questions are: how can we ensure that no more odonate habitats disappear? and how can we encourage the spread of species that are not so seriously at risk? Here are some answers:

(i) We can dig small ponds in our gardens or back yards, larger ones in our school playing areas and even larger ones in various types of open space. It will not be long before dragonflies and damselflies start to colonise them, since many species readily discover new habitats