The hosts of the species, which generally infect the coelom of their hosts, in Monocystidae family are usually oligochetes (a subclass of animals neither in the phylum Annelida nor in the Clitellata).
Oligochaeta (/lkit, -o-/) is a subclass of animals in the phylum Annelida, which is made up of many types of aquatic and terrestrial worms, including all of the various earthworms. 
