Linked from
The 34 pages that link to Parasitism, each with the reason it gives.
Biological pest controlRelated: Parasitoids develop in or on individual pests, usually killing them.
AcariRelated: Many acari exploit animals or plants, though parasitism is only one acarine lifestyle.
AgnathaRelated: Some lampreys attach to fish and feed on their body fluids and tissues.
TrypanosomaRelated: Trypanosomes depend on vertebrate hosts and often invertebrate vectors.
CoprophagiaRelated: Parasite eggs and cysts in feces can reinfect animals that consume them.