Dragonflies are amongst the largest and most spectacular insects.
They are day-flying, easy to observe and are good indicators of
unpolluted water.
Dragonflies are placed in the order ‘Odonata’ which means ‘tooth
jaws’. The adults have the largest eyes of any insect and two pairs of
large wings. There are over 5,300 species in the world.
The Life History of a dragonfly has four distinct stages: egg, larva,
pupa and adult. Eggs are laid directly into the water or into plant
tissue to protect them. The larvae hatch after 2-5 weeks, depending on
temperature. The larva is an 'eating machine' which grows through a
number of stages (instars) at the end of which it splits its skin to
grow into the next instar.
Dragonflies can remain in the larval form for one or two years, but
the length of time for those species occurring on Socotra has not been
studied.
The larva develops onto a pupa which changes from gill-breathing to
air-breathing and emerges on the stem of vegetation. It is from this
last stage that the adult insect will emerge. Adults are short-lived and
after mating and egg-laying soon die.
Dragonflies are carnivores: the larva are aggressive predators,
hunting by ambushing their prey underwater, particularly insect larvae,
fleas, snails and small fish. The adults prey on flying insects.
Amongst the animal groups on Socotra the dragonflies are not well
represented in either number of species or endemism. Just 18 species
have been recorded, only one of which, Grant's Bluet Azuragrion granti
(formerly Enallagma granti), is endemic.
Wadis with slow running or still water, small freshwater reservoirs,
cisterns and pools around leaking pipes are all good places to find
these large insects. At such sites at least six species can frequently
be seen. Amongst the better localities are the pools at Wadi Denegen,
Wadi Ayhaft, Wadi Zirage (especially at Diksam) and the small streamlets
and pools at Homhil. One species, Macrodiplax cora, is unusual in that
it frequents brackish water, and can be commonly found in coastal
lagoons and estuaries.
There have been no systematic surveys of the dragonflies of Socotra
and this would make a very useful conservation research project. This
could easily be accomplished in a few days by visiting all places with
fresh water, no matter how small.
