Earthworms are hermaphrodites.
Earthworms are simultaneous hermaphrodites, meaning worms have both male and female reproductive organs.
Despite this anatomy, most species of earthworms need a partner to reproduce.
Near the head of an earthworm is a smooth band called the clitellum. This band normally matches the color of the rest of the worm’s body, but when earthworms are ready to mate, the band turns a darker shade. Although some species of earthworms will mate on the soil surface, this leaves them exposed to predators during this vulnerable time, so most worms mate underground. The worms are thought to find one another through the release of pheromones. Once a partner is found, the two worms line up in opposite directions so that each worm’s male opening lines up with the other worm’s sperm receptacle, known as the spermatheca. The worms are then in position to exchange sperm.