Publisher Summary The organizations of both male and female reproductive systems are fairly similar. The germ cells of the reproductive organs originate from the pole cells that are among the first to differentiate during embryogenesis. Together with mesodermal tissue, they form the reproductive organs of the adult. A pair of gonads is connected by individual ducts to a common duct, constructed from both mesodermal and ectodermal origins. Both reproductive systems are coordinated by hormones and transcription factors, which are ultimately regulated by physiological and environmental factors. The chapter describes the main and accessory organs of male and female reproductive systems in insects, including development of these organs and of eggs and sperm. It also discusses the physiological processes involved in vitellogenesis, ovulation, fertilization, oviposition, and spermatogenesis, and endocrine control of these processes in insects. Although short-lived insects have a relatively brief reproductive opportunity, they compensate with a diverse assemblage of reproductive strategies that allow prodigious numbers of offspring to be produced under a wide range of ecological circumstances. In most insects, females mate with males, fertilize the eggs just before oviposition, and lay them outside of the body. This most common means of reproduction is termed oviparity. There are also some more unusual methods of producing offspring among the insects, including parthenogenesis, pedogenesis, polyembryony, functional hermaphroditism, viviparity, and hemocelic insemination.