Tiny adult worms live in the intestine of canids. They produce one gravid proglottid at a time, which detaches and passes in the feces. It ruptures and releases the eggs within it, which contaminate soil and vegetation in the vicinity.
Ungulates ingest these eggs while grazing. The egg hatches within the intestine, releasing the enclosed oncosphere. The oncosphere penetrates the intestinal wall using its hooks, and enters the bloodstream. Oncospheres are transported throughout the body, but usually are trapped in lung or liver tissue, where they begin development into a hydatid cyst. The hydatid is slow growing, taking months or years to develop. Inside the hydatid, thousands to millions of protoscoleces are produced asexually. If the hydatid is eaten by a canid, the protoscoleces are liberated and attach to the intestine, where they mature quickly. Infections of tens of thousands of adults in the definitive host are common, because infections are acquired in clumps.