Embryonated eggs passed in the feces are ingested by land snails, in which they undergo a developmental cycle. Cercariae are liberated from the snails during rainy periods and become massed in slime-balls shed on vegetation as the snail crawls. These slime-balls, each of which contains a large number of cercariae, are eaten by ants. In this host, the cercariae become encysted to form metacercariae. For humans to acquire this disease, they must ingest an infected ant.