466 for takeoff, the energy of muscle contraction must be stored temporarily as elastic energy.

This energy, at a critical point, is suddenly and rapidly released to produce the acceleration necessary to overcome gravity. Most soft-bodied larvae that crawl over, or burrow through, the substrate depend on synchronized contraction and relaxation of muscles to effect changes in body shape, the legs and accessory locomotory appendages serving simply as points of friction between the body and substrate. In these larvae the body fluids serve as a hydrostatic skeleton.

Insects that move slowly over the surface of, orthrough, water typically use ahexapodal gait. More rapidly moving species, which may be streamlined, usually employ a rowing motion of the midlegs, occasionally the hindlegs. The legs are often modified to increase the surface area presented during the active stroke and their point of insertion on the body is designed so as to obtain maximum power from the stroke. Some aquatic insects swim by other means, for example, body curling, jet propulsion, or flapping the wings.

Primitively, the direct muscles (those that connect directly with the wing articulations) are used both for supplying power for flight and for controlling the nature of the wing beat. However, in most flying insects efficiency is increased by separating the supply of power (the role of large indirect muscles in the thorax) from the control of wing beat (which remains the function of the direct muscles). In fliers that have a low wing-beat frequency, control of muscle contraction is synchronous (neurogenic); that is, there is a 1:1 ratio between wing-beat frequency (= frequency of wing-muscle contraction) and the number of nerve impulses arriving at the muscle. High wing-beat frequencies are achieved by the use of fibrillar muscles and asynchronous (myogenic) control. Fibrillar muscles always operate in antagonistic pairs. Their rhythm of contraction originates endogenously and is initiated when a muscle is stretched to a critical tension, Thus, the contractions of an antagonistic pair of fibrillar muscles are self-perpetuating, though their initiation and termination are under nervous control. The indirect muscles serve to change the shape of the pterothorax, which thus acts as an elastic box, these changes in shape causing the wings to be moved up and down. Energy released at the end of each wing stroke (when a wing's momentum rapidly decreases) is stored as elastic energy, in the wall of the pterothorax, in the resilin of the wing hinge, and (in myogenic fliers) in the fibrillar muscles. This energy is then released to power the following stroke. In most insects lift is generated through a combination of delayed stall, rapid wing rotation, and wake capture. However, in some very small species a special form of rotation-generated lift, the "clap and fling" mechanism is used. In both systems the generation of vortices, creating regions of low pressure above the wings, is a critical component. Insects use a variety of substrates as energy sources for flight. Diptera and Hymenoptera metabolize trehalose; locusts, many Lepidoptera, Hemiptera, and Odonata oxidize lipid, sometimes after an initial phase of trehalose breakdown. A few insects use proline to fuel flight. Regulation of flight metabolism is under hormonal control, with adipokinetic hormone playing a major role.

Enhanced locomotor activity, which follows receipt of a stimulus, but whose direction is without spatial reference to that stimulus, is known as a kinesis. When the direction of movement is with reference to the source of the stimulus, for example, attraction to an odor and the light-compass reaction, the movement is described as a taxis.

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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