Beef tapeworm. Coloured scanning electron micrograph (SEM) of the head of a beef tapeworm (Taenia saginata) showing the suckers it uses to cling to its host. Tapeworms are parasitic flatworms that live in the digestive tract of their vertebrate host. T. saginata is a parasite of both cattle and humans, causing taeniasis in humans. Magnification: x25, when printed 10 centimetres wide.