The Monocystinae are a subfamily of parasitic alveolates in the phylum Apicomplexa.
There are seven genera in this subfamily.
The type genus is Monocystis.
This subfamily was created by Bütschli in 1882[1] and modified by Bhatia in 1930.[2]
The species in this subfamily are cylindroid in shape with a mucron at the anterior end.
The trophozoites are solitary.
Syzygy occurs late in the life cycle.
They parasitise the coelom of earthworms and are spread by the orofaecal route.