What is the lifespan of a dragonfly
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Dragonflies: species groups - development - habitats - endangerment
|Horseshoe azure maidens during mating - they form the mating wheel typical of dragonflies|
All dragonfly species go through the same development: Egg - Prolarva - Larva - Dragonfly (Imago). In the course of their lives they live in very different habitats. The adult dragonfly lives as a flying insect on land, whereas the egg and larval stages live in the water.
In front of the egg there is of course the pairing of the male and female dragonflies, in which the male grasps the female by the head with his abdominal appendages. In this formation, which is also called tandem, the dragonflies in particular fly together to a seat. Only now does the male fill his reproductive organ with sperm. The female arches her abdomen sharply forward and brings her genital opening to the male's reproductive organ. Both animals are united in the typical "mating wheel". Depending on the species, mating takes a few minutes to around an hour.
In the case of the dragonflies, mating proceeds according to the same pattern, only that it is not carried out completely while sitting, but rather begins in flight and ends while sitting.
After mating, the eggs are laid. This takes place differently from species to species. Some dragonflies lay their eggs in tandem, with others the male protects the female from the airspace during the egg-laying process and with still other species the female lays the eggs all by herself.
But not only the way the eggs are laid varies, but also the place where they are laid. Most dragonflies attach their eggs to or stick their eggs into aquatic plants - either above or below the water. However, some species release the eggs directly into the water. Individual species are bound to very specific plants when they lay eggs, such as the green mosaic maiden. It only lays its eggs on the leaves of the rare crab claws.
The larva hatches about three to four weeks after the egg is laid; if the eggs were not laid until late in the year, they can not hatch until next spring.
|A typical life cycle for dragonflies - exemplified on the banded demoiselle (drawing D. Glitz)|
|Exuvia - this is the name given to the abandoned outer shell that remains after the larvae have hatched to form the imago (Photo: H. Cordsen)|
The first larval stage is worm-shaped and is also called the prolarve. A few minutes after hatching, the prolarva molt into the correct larva for the first time. The larvae of all dragonfly species are predatory in the water. Their prey includes various aquatic insects, small crustaceans and worms. Larger species can even prey on juvenile fish and amphibian larvae.
But you must also be careful of predators, because they are on the menu of predatory fish, other insects, amphibians and birds that hunt in the water.
The larvae moult a further seven to eleven times, depending on the species, until they finally hatch. The development time of the larva also varies from species to species. It can only last two to three months, but a maximum of about five years. This results in very different demands on dragonfly waters. Because fast-developing species can cope with summer-dry waters, while developments over several years require continuous water flow.
There are "all-rounders" whose larvae can grow up without any problems in most bodies of water. Other species are extremely demanding, for example, need clean, sandy streams or only live in spring or special moor waters. It is of course correspondingly difficult for these "specialists" because such habitats are becoming less and less.
|Large dragonfly when hatching - it can take several hours for hardening (Photo: S. Lorenz)|
When the larva is ready to hatch, it climbs up a vertical plant stem or other mostly vertical structure in the early morning and settles there. Eventually the back of its thorax and the top of its head will burst and the dragonfly will begin to push itself out of the larval skin. When it is completely hatched, it pumps its wings up with blood fluid, lets the wings harden and is finally ready for its first maiden flight.
During the hatching of the larva to the flying dragonfly, it is particularly at risk, as it has not yet hardened and its wings have not yet unfolded, so that an escape is impossible.
The lifespan of the individual dragonfly as an imago (adult flying insect) is quite short. With a few exceptions, it is only six to eight weeks. So the dragonfly spends most of its life as a larva.
After hatching, the maturation phase follows. During this phase, which can take up to several weeks, the dragonfly stays away from its developing waters, at the edges of forests or other places with a high density of insects. There it goes to catch prey for e.g. mosquitoes, caddis flies and small butterflies. Adult dragonflies themselves must be very careful against predators such as birds, spiders and wasps.
When the maturity phase is completed with the onset of sexual maturity, the dragonflies return to the waters - the circle of dragonfly life comes full circle. The females of most species stay there only briefly to mate and lay their eggs. It is the males that can be observed there for a long time, but this also differs from species to species. In some species, the males show a conspicuous territorial behavior and defend individual stream sections from other species.
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