Tissue and Organ Development 71 Appendages

Paired segmental evaginations of the embryonic ectoderm appear on the thoracic, antennal, and gnathal segments while the abdominal part of the germ band is still forming (see Figure 20.7). Their subsequent growth results from proliferation of the ectoderm as a single layer of cells and of mesodermal cells within. The cephalic and thoracic limbs ultimately differentiate into their specific form, except in eggs of secondarily apodous species where they soon shorten or become reduced to epidermal thickenings. In embryos of Muscomorpha, the thoracic appendages never develop beyond the epidermal thickening stage.

A 5 days

B 9 days

FIGURE 20.11. (A) Five-day embryo of Bruchidius (Coleoptera) after shortening of germ band. Compare this figure with Figure 20.7F; and (B) embryo of Bruchidius at hatching stage (9 days). [After D. T. Anderson, 1972b, 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.]

A 5 days

B 9 days

FIGURE 20.11. (A) Five-day embryo of Bruchidius (Coleoptera) after shortening of germ band. Compare this figure with Figure 20.7F; and (B) embryo of Bruchidius at hatching stage (9 days). [After D. T. Anderson, 1972b, 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.]

In Paleoptera and orthopteroid insects, 11 pairs of abdominal appendages evaginate before provisional dorsal closure. In most hemipteroid embryos, no sign of abdominal limbs is evident, though in those of Hemiptera and Thysanoptera appendages develop on the first and last abdominal segments. Ten pairs of abdominal evaginations develop in most en-dopterygote embryos. The fate of the abdominal appendages varies, and some or all of them may disappear before embryonic development is completed. The first (most anterior) pair disappears after blastokinesis in embryos of Paleoptera and some orthopteroid insects, but remains as glandular pleuropodia in those of Dictyoptera, Phasmida, Orthoptera, Hemiptera, and some Coleoptera and Lepidoptera. The function of the pleuropodia is uncertain, though some authors have suggested that in orthopteran embryos they secrete chitinase that brings about dissolution of the serosal cuticle. The pleuropodia are resorbed or discarded before or shortly after hatching. The appendages of the second through seventh abdominal segments are resorbed, except in some endopterygotes where they persist as larval prolegs. Pairs 8-10 may differentiate into the external genitalia or disappear, while the last pair either persists as cerci or disappears.

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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