Flukeworm life-cycle. Computer illustration showing the life-cycle of a typical fluke (class Trematode) worm. The young of this parasitic flatworm infects a mollusc, such as a snail (right), before passing to an insect carrier (ant, lower left) that feeds on the mollusc. This insect is then eaten by a larger animal (the definitive host), passing the fluke to that animal, where it reproduces and lays its eggs. Here, a cow accidentally ingests the ant whilst grazing (top) on grass (left). The fluke eggs are then passed out in the animal faeces (top left) and the cycle repeats itself.