Gas Exchange

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.]

individual cells, so that gaseous oxygen is brought into extremely close proximity with the energy-producing mitochondria.

In Calpodes ethlius caterpillars not all tracheae end in tracheoles within or on tissues. In particular, some tracheae originating from the spiracles of the eighth abdominal segment

FIGURE 15.2. Structure of (A) large; and (B) small tracheae. (C) Origin of tracheole. [After V. B. Wigglesworth, 1965, The Principles of Insect Physiology, 6th ed., Methuen and Co. By permission of the author.]

form large, greatly branched tufts that are suspended within the hemolymph (Figure 15.3). The tracheolar tips of these tufts are connected to heart and other muscles so that the tufts are constantly moved within the hemolymph (Locke, 1998). The observation that hemocytes were abundant within the tufts led Locke to speculate that the tufts are sites of gas exchange for the blood cells, analogous to the lungs of vertebrates. Though similar tracheal tufts are found in caterpillars from other lepidopteran families, their existence and function(s) among other insect groups has not been examined.

As derivatives of the integument, tracheae comprise cuticular components, epidermis, and basal lamina (Figure 15.2). Adjacent to the spiracle, the tracheal cuticle includes, the cuticulin envelope, epicuticle and procuticle; in smaller tracheae and most tracheoles only the cuticulin envelope and epicuticle are present. Providing the system with strength yet flexibility, tracheal cuticle has internal ridges that may be either separate (annuli) or form a continuous helical fold (taenidium). In large tracheae the ridges include some procuticle, but this is absent from those of tracheoles. Taenidia are absent from, or poorly developed in, air sacs. The epicuticle of tracheae comprises the same layers as that of the integument.

FIGURE 15.3. Tufts of tracheae in the eighth abdominal segment of Calpodes ethlius that perhaps serve to aerate hemocytes. Arrows indicate direction of hemolymph flow. [From M. Locke, 1998, Caterpillars have evolved lungs for hemocyte gas exchange, J. Insect Physiol. 44:1-20. With permission from Elsevier.]

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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