They are essentially reproductive factories, producing massive numbers of eggs while the lead a life of leisure in the host GI tract, consuming host-digested nutrients. One end of the tapeworm contains a head, having either suckers, hooks, or both for attachment to the host GI tract. Each proglottid segment near the end of the worm contains large numbers of eggs and is shed with feces. When ingested, proglottid eggs hatch in the GI tract of the next host to become larva and adult tapeworms. The proglottids are motile, and have been seen crawling along the floor after being passed from, e.g. a dog or cat.
Nutrition is by feeding on the blood of the host.
Anemia in heavily infected hosts is common. They usually have one or more suckers for attaching to the host GI mucosa, and do have a primitive digestive and urinary system of their own. Transmission is fecal-oral, by ingestion of contaminated water or food, development of larva and adults in the host GI tract, and shedding of eggs. Often times an intermediate host, such as a snail or fish is involved. The helminth actually absorbs host proteins onto its outer cuticle, essentially cloaking itself from the host immune system by appearing to be part of the host.