Dragonflies and their fascinating flight
Dragonfly meaning
Dragonflies along with Damselflies are belongs to the order(species) Odonata, which means ‘toothed one’ in Greek, refers to dragonfly’s serrated teeth. Dragonfly belongs to the suborder Anisoptera found commonly near the natural habitats all over the world.
They also called as devil’s arrow, devil’s darning needle and darner. Roughly around 5,000 species are found throughout the world. Scientific name of the dragonfly is Anisoptera.
Spiritual meaning of dragonfly: dragonfly symbol represents the change and transformation (dragonfly symbolism). That's why peoples tends to put dragonfly tattoo in their body.
Life cycle of dragonfly
During the first two years of their life cycle, the Laval stage (dragonfly larvae) also called ‘nymph’, they are aquatic and eat the mosquitos, tadpoles, small fishes, lavas of other insects or even larvae of their own.
Later on,
they come out from their aquatic stage, and the exoskeleton cracks to expose
the insect’s abdomen, which is packed in a long tube. After the wings come out,
they dry and get harden within hours to days, at this stage they are called
teneral which means soft or tender in Latin. Normally adults live up to six
months but some for only a few weeks.
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| Life Cycle of Dragonfly |
Body structure of dragonfly
They have a specific structure with three body parts namely head, thorax and abdomen. The head is mainly two compounds eyes composed with 28,000 single eyes, are so large and they nearly touch.
Thorax have three pairs of joined legs but most of them rarely walk properly, and two pairs of intricately veined membranous wings of two to five inches with colored markings, generally transparent.
Front and rear wings are shaped differently, this differ them from damselflies. They breath through spiracles, tiny holes in the long, thin, segmented abdomen.
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| Comparison between Dragonfly and Damselfly |
Mechanisms of flight
There are four
distinct flight styles are observed in Odonata, counter stroking (where
fore and hind wings move up and down about 180◦ out of phase), phased-stroking (where the
hind-wings cycle about 90 degrees - a quarter cycle - before the fore-wings),
synchronized-stroking (where fore- and hind-wings move in unison), and gliding.
Dragonflies are
real acrobat of the sky. They can fly upside down, fly forward and backward,
turn 360◦ on a dime, take off from different resting positions and fly more than
55 kilometers per hour to defend their territory, mate in tandem formation and
feed on live prey. Simply we can say that they are like helicopters.
Dragonfly uses counter stroking when hovering or flying slowly as this is an efficient and powerful way of flying and generates lots of lift. They adopt phased-stroking when flying about, generates more thrust but less lift compared to counter stroking.
They use
synchronized-stroking when changing the direction quickly by producing maximum
thrust. Gliding is used by some species only.
They have an unpredictable flight, they hover for a bit and take quick and sharp turns, which make them more fascinating. The most favorable thing for their variety of flight is that each of their four wings is controlled by four separate muscles attached to the wing base.
These
muscles help to change the shape of the wings and angle of attack of the wings
during each stroke. Efficient muscle action is mainly depending on the
temperature, so the dragonfly tends to maintain the temperature by spending
time and energy.
Wings of the dragonflies are not a simple
planar object; they have a very dynamic structure. Wings flexed around several
axes responding to the muscle action and inertia and the corrugations found in
the wings hold an aero foil around the physical wing, this helps to reduce the
friction.
Unlikely the fixed wings of an airplane, dragonflies have the freedom to rotate their wings to change the orientation of the wings. This help them to change the aerodynamic forces acing on the each of their four wings.
New studies show that dragonflies can adjust stroke plane orientation of each wing independently. They beat each pair of wings at a frequency of 36Hz, while the body is held almost horizontal, in two stroke planes which are almost parallel to the long axis of flight muscles and titled 60◦ relative to the horizontal.
While at
rest dragonfly’s thorax appears skewed but in-flight head held low for the
mechanical efficiency of the flight.
All dragonflies achieve their mastery of flight by varying what their wings are doing in a coordinated fashion. They can adjust wing shape, stroke length, angle of attack, move a wing forward (or backwards) of its "usual" position, stop one or two wings, adjust relationships between any two wings on either side of the body ... the list goes on.
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