Life Cycle of ODONATA -- 'the Dragonfly family'

Dragonflies (Anisoptera) and Damselflies (Zygoptera) are the odonata family. They share similarities with other insects, in that they progress from egg to aquatic larva, and, via stages (instars), to fully flying adults. Both juvenile and adult are predatory carnivores fuelled by prey and oxygen.

They are, however, very ancient - some 360 million years ancient. Thus odonata still adhere to 'incomplete metamorphosis' rather than the more modern system of complete metamorphosis - as seen in moths & butterflies.
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The latter effectively liquidate their body tissue and reconstruct themselves into a novel form that bears no resemblance
to their larval 'Caterpillar' form.

JUVENILE DONATA - Larval stage

Odonata, on the other hand, grow progressively throughout their aquatic development. As they grow they replace their exo-skeleton instar by instar. As many as 15 instars may be required to accommodate both growth and replacement of lost limbs which can regenerate at the next instar.

As the clearly visible line of development continues. Rates of growth appear to be, light and temperature, dependent. A hostile climate can be accommodated by a period of 'diapause' (cessation of development) until conditions ameliorate.

Juvenile Dragonfly larva show all the hall marks of an adult. They just gets larger and better defined at every moult
(instar). Note the compressed wing packages on the larva's shoulders which grow moult by moult throughout development. Also note the growth of the Dragon's two compound eyes which ultimately encompass some 40 thousand indiviua hexagonall lenses per eye. Excellent visual acuity is essential to the mature Dragon since it catches and consumes prey on the wing. Vast numbers of midges, mosquitoes and garden pests comprise the adult diet. Equally visual flight acuity is essential for escaping predators and engaging in breeding.

Whilst still aquatic, the juveniles absorb oxygen from water, by diffusion, either directly or by internal rectal gills (Anisoptera)
or by 3 external anal gills (Lamellae) (Zygopternan) , They feed on pond organisms as ambush predators by means of an articulated 'mask' that shoots out bearing two hooks which ensnare the prey and retract again equally fast and presenting
the prey to the mouth parts. Prey may be as large as a fish (stickleback), or a water-snail!

As larval maturity becons so larval behaviour changes and metamorphosis commences. The essence of metamorhposis is the change-over from, breathing oxygen dissolved in water to breathing air, and absorbing heat from sunlight (flight energy).

The mature Larva start to search for warmer water and a vertical support to use for metamorphosis. Initially they approach shallow, warmer water, where they can sample the air, once satisfied, they start to climb their selected emergence support. Typically they chose the cover of dusk / darkness thus limiting the risk of predation.

Under cover of darkness the larva will climb its chosen emergence support to two or three times its adult length and embed its tarsal claws in the tissue of the support. The thorax starts to expand as bodily fluids (hemolymph - analogous
to blood) are pumped to the thorax. The final instar exoskeleton starts to split across the shoulders allowing the
head /eyes and upper body to start emerging. As the exoskeleton splits wider so the wing case open and the dragons head hang down, its legs slowly emerge from the casing. Hemolyph pressure is also exerted on the lower segments expanding the dorsal split of the exoskeleton until it can hang backwards secured by its tail still within the remnant exoskeleton.

For some thirty minutes it so hangs allowing the soft legs to harden and strengthen. Hemolymph pressure is transfered to the abdomen swelling its girth and length. The white tisues that are seen are the linings of the 'treacheal tubes' (formerly used for breathing oxygen diffused from water).

The Dragon is now air breathing - falling in to the water is certain death, and predation a serious risk.

Suddenly the Dragon flip its head upright, grabs the larval case and pulls the remaining abdomen from its larval case. The abdomen expands hydraulically. The flow of hemolymp is redirected to the wing cases and they expand slowly, as the wing viens are pumped up. Result:- a fully fledged Dragon, but showing little colour but green. The entire process has taken some 2 hours. The dragon needs but sunlight and warmth to develop its 'teneral colour' and raise it's teperature for flight, this is accomplished with the assistance of wing 'whirring' to generate the energy for its maiden, dispersal flight characteristically away from water body that nurtured it..

FOOD, FIGHTING, and mating is what mature male Dragons do best....

After 'first flight' Dragons disperse, feed and prepare to compete for mates. Both sexes need to feed to build strength, and, maturity. It is imediately apparent that a dragon's spiny legs of unequall length, are useless for walking but sufficient for perching. However; their primary role is to form a basket, a shopping basket, in which aerially caught prey can be gathered within easy reach of thier powerful mandibles. (mouth parts).

Once fully fuelled and matured , the males will search out a stretch of water-body suitable for a female to lay eggs. Males will vigorously defend their chosen patch - to the death if necessary.

Any suitable female will be grabbed by the neck, behind the eyes and raped. She is unlikely to be released until the male
is satisfied that sufficient fertilised eggs have been laid in water or aquatic plants. Thereafter the male will continue serial rape for as long as he survives attrition by predators, cold, wing damage, or old age. Others will take his place until the season ends.

As you might guess the process of mating is extraodinary - the males have two sets of genitalia, more primitive insects reproduce without direct genital contact, Dragons reproduce by indirect genital contact; modern reproduction is by full genital contact. Do Dragons fill an evolutionary gap?

The Commentary (link below) goes in to greater detail.

Extra Links: Dragons > Life cycle | Commentary