After mating, slugs and snails lay their eggs on the soil or in the water, depending on the species. Each animal can lay as many as 100 eggs at a time. Eggs are very diminutive, often smaller than a pea. After two to four weeks, the eggs hatch. Despite the large number of eggs, only a few juveniles reach adult age due to attacks from several predators.
Unlike frogs, butterflies and other insects, gastropods do not undergo metamorphosis during their life cycle. The juvenile animals emerging from the eggs are very similar to the adults and already carry a shell, in the case of snails. After hatching, juveniles start to feed immediately, reaching sexual maturity at about 2 years of age, depending on species.
Some species of slugs and snails show complex mating rituals, which precedes copulation. Two adult animals contort around each other, sometimes for up to six hours. The sperm is then exchanged through the genital pore. However, some species have sharp and calcareous internal structures called "love darts," which they release against their partner during the mating ritual. The love dart penetrates the skin, releasing a substance that helps the survival of sperm when inside their body. The total life cycle of slugs and snails varies according to species, but is often about five to seven years.
Humans have used snail species for food since ancient times. The most popular species include Periwinkles in Europe, Strombus gigas in the West Indies and Haliotis in Japan. Helix aspersa and Helix pomatia are raised in farms in Europe and are used to prepare escargot. However, snails and slugs are also agricultural and garden plagues. Some slug species are also vectors to microorganisms that causes serious diseases, such as schistosomiasis.