An aedeagus (plural aedeagi) is a reproductive organ of male insects through which they secrete sperm from the testes during copulation with a female insect. Very loosely, it can be thought of as the insect equivalent of a mammal's penis, though the matter is actually quite more complex. In males of most species of Lepidoptera, the aedeagus has a sheath which is supported by an organ called the juxta, which is located between the aforementioned valvae.