Muscles And Locomotion

FIGURE 14.15. Diagram showing axes about which a flying insect may rotate.

The direction (and correlated with it, the stability) of flight necessitates the monitoring and regulation of movement in three dimensions (Figure 14.15): movement of the body in the horizontal, transverse axis is pitching; rotation about the vertical axis is yawing; and rotation around the longitudinal axis is rolling.

In Schistocerca gregaria pitching is controlled via the lift control reflex outlined above. In this species the fore and hind wings beat in antiphase. The hind wings are not capable, however, of twisting and, therefore, the value of lift generated by them is a function of the body angle (the angle at which the body is held relative to the direction of airflow). Any change in body angle, altering the lift generated by the hind wings, is compensated for by appropriate twisting of the fore wings so that the total lift produced remains constant. Other insects control pitching by varying the amplitude of the wing beat, the stroke plane (the angle at which the wings move relative to the body), or the stroke rhythm (by delaying or enhancing the moment at which pronation of the wings occurs during the beat).

The control of yawing involves sensory input from both the compound eyes and mechanoreceptors. As an insect turns, the visual field will rotate. Also, in some insects such as Schistocerca, this movement results in unequal stimulation of mechanosensory hairs at each side of the head. Yawing may be corrected by varying the angle of attack, the amplitude, or the frequency of beat, between the wings on each side of the body. All of these variables will alter the thrust generated.

Rolling is largely monitored as a result of certain visual stimuli. Commonly, the head is rotated so that the dorsal ommatidia receive maximal illumination, the source of which is normally directly overhead. Early and late in the day, however, when the latter is not the case, use is also made of the marked contrast in light intensity between the earth and

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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