Postembryonic Development

fingerlike structure, but this becomes flattened so that the central cavity is more or less obliterated, leaving only small lacunae (Figure 21.12A, B). A nerve and trachea that have been associated with the imaginal disc now grow along each lacuna occasionally branching in a predetermined pattern. At the larval-pupal molt, hemolymph pressure forces the sides of a wing bud apart so that there is sufficient space within it for the development of an adult wing (Figure 21.12C, D). During the pupal stadium extensive proliferation of the epidermal cells occurs within the wing bud, as a consequence of which the epidermis becomes folded and closely apposed over most of the wing surface. The epidermal layers remain separate adjacent to the nerve and trachea, forming the definitive wing veins (Figure 21.12E-H).

The gut of endopterygotes typically changes its form markedly during metamorphosis. In Coleoptera the foregut and hindgut undergo relatively slight modification, this being achieved by the activity of larval cells. In higher endopterygotes these regions are partially or entirely renewed from groups of primordial cells located at the junctions of the foregut and midgut and midgut and hindgut, and adjacent to the mouth and anus. The larval midgut of all endopterygotes is fully replaced as a result of the activity of either regenerative cells from the larval midgut, or undifferentiated cells at the junction of the midgut and hindgut, or both. In either arrangement, the histolyzed larval cells eventually are surrounded by adult tissue. To protect the insect from potential pathogens in the absence of a peritrophic matrix, the differentiating pupal midgut epithelium releases a mixture of antibacterial peptides into the gut lumen (Russell and Dunn, 1996).

Larval Malpighian tubules may be retained in some adult Diptera, but in other en-dopterygotes they are partially or completely replaced at metamorphosis from special cells located either along the length of each tubule or at the anterior end of the hindgut.

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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