parasite

The life cycle of the pork tapeworm Taenia solium. If a person eats pork from an infected pig that has not been properly cooked, the cysticercus attaches to the intestine and develops into an adult tapeworm. The tapeworm is a hermaphrodite and fertilizes itself, releasing proglottis, each of which may contain as many as 40,000 embryos encased in separate capsules. If the embryos are eaten by a pig, they bore from the pig's intestine into the bloodstream which carries them to the muscles, where they may be eaten by a human and the cycle continues.

Organism that lives on or in another organism (called the host) and depends on it for nutrition, often at the expense of the host's welfare. Parasites that live inside the host, such as liver flukes and tapeworms, are called endoparasites; those that live on the exterior, such as fleas and lice, are called ectoparasites.

Parasitic wasps, such as ichneumons, are more correctly parisitoids, as they ultimately kill their hosts.

The first evidence of parasites acting cooperatively to find a host was discovered in 2000 when US researchers observed around 500 larvae of the parasitic blister beetle (Meloe franciscanus) aggregating on plant stems in a formation mimicking a female bee (Habropoda pallida). When a male bee tries to mate with the mimic, the larvae cling to him and then transfer to a female bee when he mates successfully, and finally they transfer to the new nest when she lays her eggs.