Gas Exchange

flight. Odonata, for example, are generally large; movements of their thorax during wing 479

beating are pronounced and their flight muscles are of the tubular type which lack indented tracheoles. Therefore, autoventilation is extremely important in this order. In contrast, in Hymenoptera and Diptera, movements of the thorax in flight are relatively slight so that the volume change that can be achieved in the tracheal system is not significant. However, the fibrillar flight muscles of these insects are much indented with tracheoles so that gaseous oxygen is brought close to the mitochondria. Thus, in Hymenoptera simple telescopic abdominal ventilation normally creates sufficient air exchange in the thorax. In Diptera, abdominal ventilation movements are weak or non-existent, and diffusion alone satisfies the insects' oxygen requirements in flight (Miller, 1974).

Ventilation movements are initiated within and controlled via the central nervous system. Some isolated abdominal segments, provided that they contain a ganglion, can carry out normal respiratory movements, though usually an appropriate stimulus such as hy-percapnia or hypoxia is necessary to initiate the movements. The coordination of these autonomous ventilation movements and, where unidirectional air flow occurs, of spiracular valve opening and closing, is achieved by a central pattern generator (CPG) situated usually in the metathoracic or first abdominal ganglion. The nature of the CPG is not understood. However, in the desert locust, it sends bursts of impulses to each ganglion, which both excite the motor neurons to the muscles used in expiration and inhibit those going to inspiratory muscles. The activity of the CPG is modified by sensory input. For example, in the grasshopper Taeniopoda eques receptors in the central nervous system are sensitive to changing carbon dioxide and oxygen concentrations, which stimulate CPG activity so that ventilation is increased and decreased, respectively (Bustami et al., 2002).

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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