TRITOVORES

Tritovores are green-skinned humanoid insectoids with heads resembling those of flies. They communicate by clicking these mouth parts to produce sound and have simple, three-digit hands. They eat the faeces of other species. As of the 21st century, they have developed a peaceful trading space faring civilisation. They have developed telepathic translators allowing easy exchange with other species.
Source: Doctor Who Universe. (DW: Planet of the Dead)