Following on from the private lives of snails, I bring you: slugs! (The first part of this post is largely a repost of something I wrote back in 2009.)
Leopard slugs, like other terrestrial slugs & snails, are hermaphrodites. They produce both eggs & sperm, but must exchange sperm with another slug in order to fertilise their eggs. (This reproductive strategy means that an amorous snail or slug doesn’t have to find a partner of the opposite sex, it needs only to meet another snail. Or slug. Of the same species, of course.) Actual copulation is preceded by a range of somewhat slimy courtship & precopulatory displays – in garden snails this involves (among other things) piercing one’s partner with crystalline darts… Sounds painful, I know, but this part of the ritual apparently enhances uptake of the piercer’s sperm by its partner.