Life cycle of Hymenolepis spp. (right); the larval form is usually found in an arthropod. Unique to this organism is the fact that we can sustain "hyperinfections" of the species, Hymenolepis nana. This is distinct to this species and is seen in the diagram to the right. For most tapeworm infections, you only get as many adult tapeworms as larvae you ingest.
Life cycle of Echinococcus spp. (below); humans do not host the adult form, usually, dogs or other canids are the definitive hosts. The usual intermediate host is a rodent, but humans can become intermediate hosts by accidentally ingesting the eggs. Echinococcosis can be extremely dangerous as the larval forms can grow very large in many areas of the body. The larval form is known as a hydatid cyst. This life cycle is to the bottom right.
