Reproduction takes place as the result of many processes that occur sequentially in time and are different in nature. The first of these is sexual differentiation, which includes the organization of the genital organs, the formation of exit ducts for sexual products, the development of secondary sexual characters, and subsequent spermatogenesis and oogenesis. Oogenesis in turn includes several successive phases—gonial mitoses, the entry of the gonocytes into meiosis, and the differentiation of the ovarian follicles within which vitellogenesis occurs and the chorion is formed. The male-female encounter leading to mating is preceded or accompanied by the release of pheromones and by special courtship behavior patterns. Mating sometimes takes place before vitellogenesis, sometimes follows it and precedes egg laying. It exerts a stimulatory role on these two processes through the secretions of the male accessory glands (possibly prostaglandins, Loher, 1979), which are transmitted to the female during mating. Egg laying does not generally occur at random; some females display a circadian egg-laying rhythm, while others select their laying site in accordance with the food requirements of the larva that will hatch from the egg.
KeywordsVentral Nerve Cord Neurosecretory Cell Stick Insect Abdominal Ganglion Secondary Sexual Character
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