10

N. Chari and P. Srinivas

Osborne [4] interpreted Magnan’s Data for giving elaborate mathematical treat-

ment for understanding the flight characteristics. He assumed that the force developed

by the wingbeat is proportional to the square of the velocity of the forward flight.

He also derived a general equation for the lift and drag coefficients (CL and CD).

Roeder [5] studied the thoracic movements and electro-potential variations in flight

muscles of insects during flight. He also used the piezoelectric phonograph method

for studying the wingbeat frequency. Sotavalta [6] reported the essential factors

regulating the wingbeat frequency of insects due to wing mutilation and loading.

Chadwick [7] reviewed the motion of insect wings. He reported an increase in wing-

beat frequency with age and temperature in Drosophila. Sotavalta [8, 9] has analysed

the wing stroke frequency and conducted mutilation studies and suggested the terms

such as Neurogenic (Synchronous) and Myogenic (Asynchronous) fliers. There is

also a difference in the structure and physiology of these muscles including tracheal

supply and metabolic pathways.

Weis-Fogh and Jensen [10] elucidated the basic principles of insect flight on the

basis of biology and physics of flight of desert locust, Schistocerca gregaria. They

analysed wing kinematics using polar curves and calculated lift and drag coefficients

(CL and CD). This is one insect where the morpho-functional relation of flight appa-

ratus and aerodynamics has been relatively well understood. Weis-Fogh and Jensen

[10] further explained the aerodynamics by using the blade element analysis. He

concluded that for a tethered desert locust, the downstroke of the wings was respon-

sible for both lift and thrust production. The upstroke is more or less a recovery

stroke and does not require much metabolic energy. Pringle [3] in his book on Insect

Flight reviewed the basic anatomy and physiology of pterothorax of various insect

fliers. Greenwalt [11] opined that the wings of birds and insects may be assumed as

mechanical oscillators and developed a differential equation for computing the wing-

beat frequency in hovering. Greenwalt subsequently based his study on wing length

and expressed millimetre as a basic unit in his calculations. However, the derived

equation for calculating hovering frequency is quite complex. Sotavalta [12] has

analysed the flight acoustics and wingbeat frequency of Bombus, a Hymenoptera.

Anderson and Weis-Fogh [13] have described resilin elastomere protein which is

found well developed at the base of the wings and is responsible for the feasibility of

high-frequency flight in insects. Recently, molecular cloning techniques have been

used for constructing resilin-based proteins. A number of formulae as suggested by

various authors for the calculation of wingbeat frequency based on flight parameters

have been discussed by Chari [14]. In hovering flight weight of the flier is equal to

lift and lift is proportional to hovering frequency.

Bennett [15] studied the wing of Melolantha as a model for the study of flight

kinematics. He emphasized the significance of unsteady flow over the airfoil of a

flying insect. Vogel [16] has showed that inertia of the boundary layer could be a

significant factor for the mechanics of Resonant-Wing-Thorax System of insects. He

also studied the flight kinematics of Drosophila by using a photographic technique.

Pennycuick [17] has explained hovering flight by using a helicopter model. Crawford

[18] proposed a relation for the wingbeat frequency of small flier in hovering based on

Newton’s laws. He presented a theoretical relation for wingbeat frequency depending