An aedeagus (plural aedeagi)'s a reproductive organ of male insects through which they secrete sperm from the testes during copulation with a female insect. The sperm contains capsules called spermatophores, which contain the spermatozoa. In addition to the spermatophores, in some insect species the aedeagus also discharges a spermatophylax, which serves as a nutrient to the female. The aedeagus's part of the male's abdomen, which's the most caudal (hindmost) of the three segments of an insect.… (More on Aedeagus)