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Image: Liz Noffsinger / FreeDigitalPhotos.net |
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How is it that the dragonfly can perform its energetically-demanding aerial
acrobatics — flying backwards or forwards, fast, slow or hovering
— and remain airborne for such extended periods?
The answer, in part, is that it has four wings.
While many flying insects use only a single pair of wings
(and very well, too)
1 , dragonflies have ‘unusual musculature’ that
allows them to move each of their four wings
2 independently, which is a key
factor in their ability to perform ‘astonishing
acrobatics’
3 .
It had been thought that such out-of-phase flapping comes at a cost, i.e.
reducing the amount of lift the insect can generate.
However, bioengineers have built a robotic version of a dragonfly, attaching
sensors at the base of the robot’s wings to record lift and drag forces,
allowing researchers to calculate aerodynamic efficiency.
4,5 And it turns out
that in out-of-phase flapping, the hind wings can extract extra energy from
the wake of air sent by the front wings, reducing aerodynamic power
requirements by up to 22% compared with a single pair of wings. This
mechanism, the researchers explained, ‘is directly analogous to that
exploited by coaxial contra-rotating rotors, exemplified by helicopters such
as the Kamov Ka-50.’
4
What’s more, dragonflies have the flexibility to switch between
out-of-phase flapping and in-phase flapping as appropriate. When taking off,
for example, real dragonflies synchronise their wing beats, thus they are able
to lift and accelerate better than if they used only two wings or four
out-of-sync wings.
With this new insight into the aerodynamic efficiency of out-of-phase
flapping, engineers hope to apply it in the next generation of flapping micro
air vehicles. As one bio-engineer explained, battery life limits how long
micro air vehicles can stay aloft, so ‘any tips or tricks which enhance
aerodynamic efficiency will be warmly welcomed.’
5
It defies reason to suggest that an energy-efficient aerial acrobat such as
the dragonfly was not intentionally, and intelligently, designed.
In fact, the researchers involved in this aerodynamic efficiency study
apparently recognized the difficulty their finding presents to the
widely-accepted evolutionary scenario, which posits that four-winged
dragonflies arose long before (i.e. are ‘more primitive’ than) the
two winged Diptera:
‘Caution must be applied when interpreting the biological significance
of the above observations. Suggesting an evolutionary advantage to either
two-winged or four-winged forms is unwise, considering the success and
diversity of the true flies (Diptera), and yet the maintenance of the
four-winged form by dragonflies since the Carboniferous.’
4,6
Surely it makes much more sense to say that four-winged dragonflies and
two-winged flies were each designed to do what they do do, and what they do
do, they do do well!
- See creation.com/fly. return to text
- Only damselflies and dragonflies have four wings capable of being moved
independently. Certain other insects, such as butterflies, bees and cicadas,
have four wings but they synchronize the motion of the two pairs so that the
effect is akin to having just two wings. return to text
- See creation.com/dragonfly return to text
- Journal of the Royal Society Interface, doi:10.1098/rsif.2008.0124, 13 May
2008. return to text
- ScienceNOW Daily News, <sciencenow.sciencemag.org/cgi/content/full/2008/514/4>,
14 May 2008. return to text
- The fact that living and fossil forms are the same despite the supposed
‘millions of years of evolution’ in the meantime is a major
challenge to evolutionists, though they don’t always admit it. See creation.com/stasis. return to text
Courtesy of Creation Ministries International. <CREATION.com>
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