any one of numerous species of cestode worms belonging to taenia and many allied genera. the body is long, flat, and composed of numerous segments or proglottids varying in shape, those toward the end of the body being much larger and longer than the anterior ones, and containing the fully developed sexual organs. the head is small, destitute of a mouth, but furnished with two or more suckers (which vary greatly in shape in different genera), and sometimes, also, with hooks for adhesion to the walls of the intestines of the animals in which they are parasitic. the larvae (see cysticercus) live in the flesh of various creatures, and when swallowed by another animal of the right species develop into the mature tapeworm in its intestine. see illustration in appendix.