Adults live in the tissues of birds and mammals. These are for most species the mucosa of some portion of the gastrointestinal tract, but for others it is an internal organ such as the liver. Unembryonated eggs pass in the feces or are released from the host's carcass after decomposition or predation (in which case they pass in the predator's feces). An L1 develops within the egg and is infective to another host if ingested. Then it hatches, migrates to its final site, and undergoes 4 molts to become an adult. While the embryonated egg is on the ground, if it is ingested by an earthworm, it may hatch and the L1 enters the body cavity, waiting to infect a suitable host if the earthworm is eaten.