Parasitism is a type of symbiotic relationship. In this relationship the parasite, a kind of predator, lives on the surface of or inside a host, from which it gets its nourishment. The parasite benefits at the expense of the host. In many parasitic cases, the host is harmed. However, in other parasitic relationships, the host isn’t injured, but doesn’t benefit either. Ants, such as those shown in the picture here, are one of the organisms in which the parasitic fluke (also known as a flatworm or trematode) Dicrocoelium dendriticum (Lancet liver fluke) thrives. Adult Lancet liver flukes are hermaphrodites, and pass the live eggs out as feces. The eggs are eaten by snails. They eventually form cercaria, which are released to the outside as slime balls. These slime balls are eaten by ants; once ingested, the cercaria move to the ant’s abdomen and some move to the brain. When they are in the brain, ants move up on the tops of vegetation and stay paralyzed for about one-two months. These ants are often eaten by sheep, cattle and other animals, in which the flukes can develop into adults and start the cycle again.