Viviparity

Viviparity, the retention of developing offspring within the maternal genital tract, is found in a range of complexity within the Insecta. It is seen in different forms in species from several orders, but among Diptera the entire range of variation may occur.

In its simplest form (ovoviviparity) the eggs retain their full complement of yolk for nourishment of the embryo. The eggs may be retained within the mother for a varied period of time but usually are laid just before they hatch. Such an arrangement is seen in many Tachinidae (Figure 20.15) where the first-instar larvae actually escape from the chorion during oviposition. Associated with retention of the eggs, which presumably affords them greater protection, is a trend toward production of fewer of them. As fewer eggs are produced each can acquire more yolk so that larvae can hatch at more advanced stages of development. For example, many Sarcophagidae (flesh flies) produce only 40-80 eggs but are larviparous; that is, larvae hatch from the eggs while the latter are still within the reproductive tract. At the extreme, the number of eggs that mature simultaneously is reduced to one, as, for example, in Hylemya strigosa (Anthomyiidae) and Termitoxenia sp. (Phoridae). In Hylemya

FIGURE 20.13. Early development of Litomastix (Hymenoptera). (A) Fertilization; (B) first cleavage; (C) two-cell stage; (D-F) next stages; (G) formation of spindle cells; and (H) formation of secondary embryonic masses. [After O. M. Ivanova-Kasas, 1972, Polyembryony in 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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