Tracheae and Tracheoles

In apterygotes other than lepismatid Zygentoma, the tracheae that run from each spiracle do not anastomose either with those from adjacent segments or with those derived from the spiracle on the opposite side. In the Lepismatidae and Pterygota both longitudinal and transverse anastomoses occur, and, though minor variations can be seen, the resultant pattern of the tracheal system is often characteristic for a particular order or family. Generally, a pair of large-diameter, longitudinal tracheae (the lateral trunks) run along the length of an insect just internal to the spiracles. Other longitudinal trunks are associated with the heart, gut, and ventral nerve cord. Interconnecting the longitudinal tracheae are transverse commissures, usually one dorsal and another ventral, in each segment (Figure 15.1). Parts of the tracheal system, for example, that of the pterothorax, may be effectively isolated from the rest of the system by reduction of the diameter or occlusion of certain longitudinal trunks. This arrangement is associated with the use of autoventilation as a means of improving the supply of oxygen to wing muscles during flight (Section 3.3). Also, tracheae are often dilated to form large thin-walled air sacs that have an important role in ventilation (Section 3.3) and other functions.

Numerous smaller tracheae branch off the main tracts and undergo progressive subdivision until at a diameter of about 2-5 they form a number of fine branches each 1 or less across known as tracheoles. Tracheoles are intracellular, being enclosed within a very thin layer of cytoplasm from the tracheoblast (tracheal end cell) (Figure 15.2), and ramify throughout most tissues of the body. They are especially abundant in metabolically active tissues. Thus, in flight muscles, fat body, and testes, for example, tracheoles indent

FIGURE 15.1. (A) Dorsal tracheal system of abdomen of locust; and (B) diagrammatic transverse section through abdomen of a hypothetical insect to illustrate main tracheal branches. [A, from F. O. Albrecht, 1953, The Anatomy of the Migratory Locust. By permission of Athlone Press. B, from R. E. Snodgrass, Principles of Insect Morphology. Copyright 1935 by McGraw-Hill, Inc. Used with permission of McGraw-Hill Book Company.]

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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