Flea tapeworm. Coloured scanning electron micrograph (SEM) of a flea tapeworm (Dipylidium caninum), showing its head (top). Tapeworms are parasitic flatworms that live in the digestive tract of their vertebrate host. D. caninum is a cyclophyllid cestode worm that infects organisms afflicted with fleas and canine chewing lice, including dogs, cats, and pet-owners, especially children. Magnification: x40, when printed 10 centimetres tall.