What kind of parasite is the tapeworm?
Cestoda
All cestodes are parasitic; many have complex life histories, including a stage in a definitive (main) host in which the adults grow and reproduce, often for years, and one or two intermediate stages in which the larvae develop in other hosts. Typically the adults live in the digestive tracts of vertebrates, while the larvae often live in the bodies of other animals, either vertebrates or invertebrates. For example, Diphyllobothrium has at least two intermediate hosts, a crustacean and then one or more freshwater fish; its definitive host is a mammal.  Some cestodes are host-specific, while others are parasites of a wide variety of hosts. Some six thousand species have been described; probably all vertebrates can host at least one species.