The zama fly was an apparently non-sentient insectoid species native to the planet of the Ugrakks. They were massive in comparison to Earth flies. The average adult human was smaller than one of a zama fly's legs.
As Professor Lammers noted to the Third Doctor, they were an enemy of the Ugrakks. Because the Ugrakks held dominion over the flora of their planet, they were able to use equally huge flowers to fire deadly spores against zama flies who approached the Ugrakk city.