In the female insect, the spermatheca is an ectodermal organ responsible for receiving, maintaining, and releasing sperm to fertilize eggs. The number and morphology of spermathecae vary according to species. Within the spermathecal lumen, substances in the semen and secretions from the spermathecal gland nourish the sperm. Thus, the spermatheca provides an appropriate environment that ensures the long-term viability of sperm. Maintaining sperm viability for long periods within the spermatheca is crucial for insect reproductive success; however, the details of this process remain poorly understood. This review examines several aspects of and gaps in the current understanding of spermatheca biology, including morphology, function, reservoir filling, development, and biochemistry. Despite the importance of the spermatheca in insects, there is little information on the gland secretions and their role in the maintenance and protection of male gametes. Furthermore, in this review, we highlight the current information on spermathecal gland secretions and the likely roles they play in the maintenance and protection of sperm.