Dragonflies have inhabited the Earth for about 250 million years. They were one of the first species of
winged insects to evolve.
They are wonderful fliers and have exceptional vision.
There are about 5,000 species worldwide and their life-cycle can be anything from a few weeks to a few months
(and they can live for a few years as a nymph or larva before emerging).
A large percentage of a dragonfly's brain power is devoted to sight. Its two large compound eyes give it nearly
360 degree vision and their colour vision is superior to that of humans.
Their antennae are very small since they do not have much of a sense of smell.
There is evidence that a few species migrate, probably in response to environmental changes.
In adulthood they are essentially a fresh-water species although there is one species in North America
(seaside dragonlet) that lays its eggs in salt water.
They are very acrobatic insects that cruise at about 10mph but are capable
of reaching about 30mph. Damselflies are much slower, however.
They are extremely manoeuvrable and can hover or make quick turns in any direction.
Some eggs hatch a few weeks after laying, some after a few months. There are also instances where the eggs over-winter and hatch in the spring. Soon after emerging from the egg and existing briefly as a very small worm-like creature the insect rapidly goes through several stages of larval growth. The number of stages and the length of time before emerging from its larval casing varies considerably depending upon species. Finally the larva climbs from the water using a plant stem and attaches itself to it. Its shell, known as an exuvia, eventually breaks and the insect starts to emerge. First the thorax, then the abdomen. The emerging creature expands as it develops making it look as though it would have been impossible to fit into the exuvia. When the insect has fully emerged it has to wait for its wings to become strong enough to enable it to fly off. At this time, it is at its most vulnerable and is referred to as a teneral. Its wings are very shiny and the colours of the body, eyes and wing-spots etc. are not developed.
It is a common sight to see two damselflies (less often, dragonflies) flying together (in tandem).
The male damselfly grasps the female by the neck with the claspers at the end of his abdomen.
With dragonflies, the male grasps the back of her head.
This is the preliminary stage before mating takes place. There is little sign of courtship.
Mating can start almost immediately in the air or the couple fly to the ground, a perch or vegetation.
Mating is often described as the pair being 'in cop' (short for copulation).
The male has a genital opening near the end of his abdomen. Some time before mating he bends his
abdomen in order to transfer sperm from his genitals to 'accessory genitalia', situated further up his abdomen.
One of the functions of these accessory organs (during mating) is to clean out sperm from any previous couplings that
the female might have had so that the male can be sure that it is his sperm that will fertilise her eggs.
Once the female has been seized and the pair is in tandem, the male bends his abdomen until
she can bring her genitals (near the tip of her abdomen) in contact with his 'accessories'.
The couple are then said to be in a 'wheel' or 'heart' position.
The act itself lasts a few seconds or a few hours, depending upon the species.
Egg laying occurs very soon after mating finishes. Pairs (usually damselflies) often stay
together in tandem during egg-laying so that the male can guard the female.
The female lays eggs (oviposits) shortly after mating. She may do this on her own or the mating pair may stay together (in tandem) so that she has some protection. Sometimes the pair separates but the male stays nearby to ward off attempts to interfere with the laying. This depends on the species. In general, damselflies remain attached but dragonflies oviposit on their own. The eggs have two different shapes, either spherical or elongated, again depending upon species. The former are laid into water, the other type are laid into plants. The female lays many eggs in batches during her lifetime.
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A dragon undergoes many changes in form and colour as it passes from its emergent stage, into adulthood and old age.
Perhaps the most intriguing is the blue-tailed damselfly, with its five possible female forms
A freshly emerging insect is referred to as a teneral.
Its wings are shiny and soft and it has to wait until they are hard enough for it to make its maiden flight.
Its colours are weak, wing-spots are clear and the abdominal segments do not have a strongly defined pattern.
As it passes from teneral to immaturity and into adulthood the insect often undergoes a number of colour changes.
In some cases these can be quite dramatic.
For example, the abdomen of the male broad-bodied chaser changes from yellow to blue. Similarly, the male
black-tailed skimmer. When some female species age they tend to adopt male colouring, which is a
surprising transformation.
Photos show that dragons will eat almost any flying insect, including butterflies
and moths. They will even eat other dragonflies and damsels if they're small enough.
Their legs are not suitable for walking, but they are used for grabbing flying insects and
when pushed forward they create a sort of basket in which to contain the prey while they eat it.
But, of course, dragons fall prey to other insects.
They are very vulnerable just after they leave their larval casing. Adults are predated mainly by birds
(hobbies eat many). They also get caught in spiders' webs.
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clue: 
dragonfly
[ drag-on, plus 'fly' (knowing) ] |
| A | emergence | E | portraits | |
| B | feeding | F | in flight | |
| C | ovipositing | G | in tandem | |
| D | mating | + | extra(s); hover cursor over '+' sign for info. |
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