Parasite is an organism that lives on or in an organism of another species, known as the host, from the body of which it obtains nutrient.Bed bugs are parasitic insects of the cimicid family that feed exclusively on blood. Cuscuta is a genus of about 100-170 species ofyellow, orange, or red (rarely green) parasitic plants. Leeches and Lichens are also organisms in the group of parasites.