Mating,insemination, and ovulation in the tsetse fly, Glossina morsitans

Virgin females of the tsetse fly, Glossina morsitans orientalis, retain their first egg within the right ovary whereas mated females ovulate. The component of the mating act which causes ovulation and thereby initiates the ovarian cycles which follow, is not insemination, the construction of a spermatophore in the uterus, or a humoral factor associated with the testes, accessory glands or ejaculatory ducts of donor males, or ‘full’ spermathecae of donor females. The ovulation rate increases with copulation time and females are shown to ‘add up’ their ‘sexual experience’ independently of that of the males. Inter-specific matings between G. morsitans and G. austeni also result in ovulation, but an unidentified factor associated with the completion of the mating act was also apparent. It is suggested that a ‘mechanical’ factor probably with nervous and endocrine components is responsible for the release of the egg from the ovary. Observations on the construction of empty spermatophores by aspermic males of G. morsitans are included.