Reproductive System

The reproductive system includes both mesodermal and ectodermal components. In female exopterygotes, the vagina and spermatheca develop after hatching as midventral ectodermal invaginations of the seventh or eight abdominal segment. In males, the ejaculatory duct and ectadenes (ectodermal accessory glands) are formed from a similar midventral invagination of the ectoderm of the ninth or tenth abdominal segment.

The paired genital ducts and mesadenes (mesodermal accessory glands) arise in exopterygotes from mesoderm of the splanchnic walls of certain abdominal somites which first thickens than hollows out to form coelomoducts. Some of these soon disappear, but those of the seventh and eighth somites (in females) or ninth and tenth somites (in males) enlarge to form the ducts and/or accessory gland components. In endopterygotes, the genital ducts are formed during postembryonic development. In Drosophila and other muscomorph Diptera the reproductive system (excluding the gonads) develops from a single or pair of imaginal discs during metamorphosis (Chapter 21, Section 4.2).

Development of the gonads varies, though two related trends can be seen, namely, earlier segregation of the primordial germ cells and restriction of these cells to fewer abdominal segments. In the most primitive arrangement, seen in some thysanuran and orthopteran embryos, the germ cells do not become distinguishable until they appear in the splanchnic walls of several abdominal somites. In Locusta embryos, for example, they are found initially in the somites of abdominal segments 2-10, though they remain only in segments 3-6. Eventually they fuse longitudinally to form a compact gonad on each side. Such a segmental arrangement is presumably primitive as it is seen also in adult Annelida, Onychophora, Myriapoda, and non-insectan apterygotes (Anderson, 1972a).

In embryos of Dictyoptera, Phasmida, Embioptera, and Heteroptera the germ cells become apparent early in gastrulation. Nevertheless, they still become associated with the splanchnic mesoderm of several anterior abdominal segments.

In embryos of Dermaptera, Psocoptera, Thysanoptera, homopterans, and endoptery-gotes, the germ cells differentiate as the blastoderm forms (see Figure 20.3B). After somite formation, they migrate to abdominal segments 3 and 4 in exopterygote embryos or abdominal segments 5 and 6 in endopterygote embryos where they divide into left and right halves and become surrounded by splanchnic mesoderm.

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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