Embryonic Development

FIGURE 20.7. Stages in elongation and segmentation of germ band in Zootermopsis (Isoptera) (A-C) and Bruchidius (Coleoptera) (D-F). [After D. T. Anderson, 1972a,b, The development of hemimetabolous insects, and the development of holometabolous insects, in: Developmental Systems: Insects, Vol. I (S. J. Counce and C. H. Waddington, eds.). By permission of Academic Press Ltd., and the author.]

cells soon separate from the outer layer, which closes to obliterate the groove. It is from the anterior and posterior points of closure of the gastral groove that the stomodeum and proctodeum, respectively, develop. The outer layer can now be distinguished as the embryonic ectoderm. The invaginated cells, which proliferate and spread laterally, form the mesoderm (Figure 20.9B,C) except adjacent to the developing stomodeum and proctodeum where they become the anterior and posterior midgut rudiments, respectively. The meso-dermal cells become concentrated into paired longitudinal tracts which soon separate into

FIGURE 20.8. Early embryonic development in Calopteryx to show anatrepsis andkatatrepsis. [A-E, after O. A. Johannsen and F. H. Butt, 1941, Embryology of Insects andMyriapods. By permission of McGraw-Hill Book Co., Inc. F, After R. F. Chapman, 1971, The Insects: Structure and Function. By permission of Elsevier/North-Holland, Inc., and the author.]

FIGURE 20.8. Early embryonic development in Calopteryx to show anatrepsis andkatatrepsis. [A-E, after O. A. Johannsen and F. H. Butt, 1941, Embryology of Insects andMyriapods. By permission of McGraw-Hill Book Co., Inc. F, After R. F. Chapman, 1971, The Insects: Structure and Function. By permission of Elsevier/North-Holland, Inc., and the author.]

segmental blocks, leaving only a thin longitudinal strip, the median mesoderm, from which hemocytes later differentiate. From these segmental blocks, paired hollow somites usually arise (Figure 20.9E). Somite formation is initiated and occurs more or less simultaneously in the gnathal and thoracic segments, spreading anteriorly and posteriorly after gastrulation takes place. Formation of the coelom (the cavity within a somite) may occur in one of two ways, by internal splitting of a somite or by median folding of the lateral part of each somite.

FIGURE 20.9. Formation of gastral groove, somites, and embryonic membranes. [After D. T. Anderson, 1972a, The development of hemimetabolous insects, in Developmental Systems: Insects, Vol. I (S. J. Counce and C. H. Waddington, eds.). By permission of Academic Press Ltd., and the author.]
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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