Dragonfly Flight
Odonates are high performance fliers! Some can reach speeds of up to 35 mph or more and travel as much
as 85 miles per day. They can fly forward and backward, hover for long
periods of time and execute quick maneuvers better than any jet
fighter. Their excellent flying
abilities have given them the ability to forage widely for food, make
quick escapes from predators and search actively for mates. It is thought
that their unique aerodynamic design has helped to keep them around for some 300 million years.
So How Do They Do This?
To understand how an odonate
flies, we need to know a little bit about their anatomy. Odonates have
four wings, two on each side of their thorax.
Although the wings look fragile, they
are actually very strong and flexible. Each wing is supported by a
net-like framework of veins. These veins are heavier, stronger and closer
together toward the leading edge and thinner and more
flexible toward the trailing edge. This makes the
insect's wings a well constructed system capable of supplying both
propulsion and lift while minimizing drag. The nodus near the center of the leading edge allows for some flexibility.;
The stigma at the wing tips
are thought to add weight to the wing eliminating vibration during flight.
Each wing of the
dragonfly operates independently of the others. Each pair of
wings normally beat together but the hindwings usually beat first; then the forewings
start their downstroke. Dragonflies twist their wings on a downstroke, creating small tornadoes of air
. This air runs along the leading edge of the
forewing creating lift that keeps them flying. The hindwings catch
these swirls of wind and add even more a lift. Tiny hair-like
projections on the surface of the wings monitor airspeed.
Dragonflies can employ several
different kinds of wing beat patterns to suit the situation.; If they are
threatened by a predator and need to make a fast escape, they can switch to a
synchronized wingbeat, where all four wings beat downwards at the same time
for a burst of speed. On the other hand, when a dragonfly
needs to slow it down and hover it can do so by switching to independent wingbeats, maintaining lift while adjusting its position precisely.
Recently researchers
have begun to employ state of the art technology when studying the wing motions of insects
during flight. They can now calculate how much oxygen and fuel they use.
By monitoring a dragonfly's metabolism, we have learned that flying
requires an enormous amount of energy. According to some authorities,
a dragonfly uses 100 times more energy in flight than at rest.
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