Page 32 - Design in Nature

30 DESIGN IN NATURE

System Behind the Thrusting Force
It is not enough to flap wings up and down in order to maintain
smooth flight. The wings have to change angles during each flap to create a
force of thrust as well as an up-lift. The wings have a certain flexibility for
rotation depending on the type of insect. The main flight muscles, which
also produce the necessary energy for flight, provide this flexibility.
For instance, in ascending higher, these muscles between wing joints
contract further to increase the wing angle. Examinations conducted
utilising high-speed film techniques revealed that the wings followed an
elliptical path while in flight. In other words, the fly does not only move its
wings up and down but it moves them in a circular motion as in rowing a
boat on water. This motion is made possible by the main muscles.
The greatest problem encountered by insect species with small bodies
is inertia reaching significant levels. Air behaves as if stuck to the wings of
these little insects and reduces wing efficiency greatly.
Therefore, some insects, the wing size of which does not exceed one
mm, have to flap their wings 1000 times per second in order to overcome
inertia.
Researchers think that even this speed alone is not enough to lift the
insect and that they make use of other systems as well.
As an example, some types of small parasites, Encarsia, make use of a
method called "clap and peel". In this method, the wings are clapped
together at the top of the stroke and then peeled off. The front edges of the
wings, where a hard vein is located, separate first, allowing airflow into the
pressurised area in between. This
flow creates a vortex helping
the up-lift force of the wings
clapping. 9
There is another special
system created for insects to
maintain a steady position in the air.
Some flies have only a pair of wings
Encarsia and round shaped organs on the back called
halteres. The halteres beat like a normal wing