Venom Grub

Venom Grubs are the two (possibly related, or even the same) species, one encountered by the First Doctor, another was told of to the Ninth Doctor.

Vortis Venom Grubs
The Vortis Venom Grubs were encountered by the Doctor on the planet Vortis in the Isop galaxy. They are the living weapons of the Zarbi, an ant-like race, used in a war against the Menoptra. (DW: The Web Planet)

Slitheen Venom Grubs
The Slitheen Venom Grubs are a Venom Grub species used by the Slitheen Family. These Venom Grubs are used to dispose of unwanted members. Blon claimed that if she didn't follow the criminal activities of the rest of the family, she would have been fed to the Venom Grubs. (DW: Boom Town)


 * If these two types of Venom Grub are related it may mean the Slitheen have inter-galactic capabilties. However, it may just be simply a concidence.