Muscles And Locomotion

and, therefore, the wing to be lowered (Figure 14.14B). In Coleoptera and Orthoptera some power for a downstroke is also obtained by contraction of the basalar and subalar muscles and in Odonata and Blattodea, this power is derived entirely from contraction of these direct muscles. The points of articulation of these muscles with the wing sclerites lie outside the pleural wing process so that when the muscles contract the wing is lowered (Figure 14.14C). In all insects, however, the basalar and subalar muscles are important in wing twisting, that is, altering the angle at which the wing meets the air, thereby affecting the values of the lift and thrust generated. Contraction of the basalar muscles causes the anterior edge of the wing to be pulled down (pronation), whereas contraction of the subalar induces supination (the pulling down of the posterior edge of the wing). Contraction of the other direct muscle, the wing flexor, causes the third axillary sclerite to twist and to be pulled inward and dor-sally. This pulls the vannal area of the wing (Figure 3.27) up over the body and enables the wing to fold along predetermined lines (usually the anal veins, and vannal and jugal folds). Unfolding (extension) of the wing occurs when the basalar muscle contracts.

Early descriptions of the role of muscles in wing flapping envisioned the muscles as supplying power directly to the wings to effect the wing beat. Thus, the speed with which muscles could contract would determine the speed at which a wing was lowered or raised. In turn, this determined the value of the lift generated. Not until the 1950s was it realized that a critical feature is the ability to store a large proportion of the energy released at the end of each stroke, when a wing's momentum is rapidly reduced. The momentum is reduced by (and the energy stored in) elastic structures. Then, in the following stroke the elastic energy is used to power wing movement, making the process remarkably efficient. For example, because the upstroke is aided by the pressure of the onrushing air on the underside of the wing, only a small amount of the stored elastic energy is used to raise the wing. The remainder (about 86% in the desert locust) is then used to power the following downstroke (Pringle, 1974). In insects that use synchronous muscles to generate power, the principal sites for storage of elastic energy are the lateral walls of the pterothorax and the resilin-containing hinge between the pleural wing process and second axillary sclerite. However, in insects that have fibrillar muscles with their greater elasticity (i.e., use asynchronous control of muscle contraction) the energy is mainly stored in the muscles themselves.

Beekeeping for Beginners

Beekeeping for Beginners

The information in this book is useful to anyone wanting to start beekeeping as a hobby or a business. It was written for beginners. Those who have never looked into beekeeping, may not understand the meaning of the terminology used by people in the industry. We have tried to overcome the problem by giving explanations. We want you to be able to use this book as a guide in to beekeeping.

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