Metatraxi

Metatraxi were an insectoid species.

Metatraxi ate their parents on hatching. (BNA: Down)

Garpol once bought a lawn mower off a Metatraxi. (VD: Question Mark Pyjamas)

The Krotons went to war with the Metatraxi, during which they devastated their homeworld. (EDA: Alien Bodies)

Behind the Scenes
Originally, the Metatraxi were to be featured in Earth Aid, a script written by Ben Aaronovitch for the Seventh Doctor in the cancelled Season 27. In this story, they would have been seen to be forcing their enemies through all methods, particularly bargaining, to take a weapon, as a problem in their mental complex was that they could not harm un-armed opponents.