Publisher Summary This chapter discusses accessory glands of both female and male insects. Accessory glands of reproductive systems produce secretions that aid in sperm maintenance, transport, and fertilization. In addition, accessory glands in females provide protective coatings for eggs. The interplay between male and female secretions from accessory glands is a key element in the design of diverse mating systems. Accessory gland secretions can have digestive functions important in sperm management. Sperm management by females involves a wide range of processes, including liberation of sperm from a spermatophore, digestion of male secretions and sperm, transport of sperm to and from the spermatheca, maintenance of stored sperm, and fertilization. Further, the effects of male accessory gland secretions on the female are best known for the fruit fly, Drosophila melanogaster, in which the functions of several gene products have been explored at the molecular level. Since insects have a diversity of mating systems, the specific functions of accessory gland secretions are likely to reflect this variation.