Mosquito

Mosquitoes were non-sentient insects native to Earth.

The Fifth Doctor claimed that the London Underground had its own unique species of mosquito. (PROSE: Light at the End of the Tunnel)

The First Doctor and Steven Taylor killed a giant alien mosquito on Earth. Its remains combined with snow and the DNA of two human boys, causing the two snowmen they had made with their mother to come to life. They were rescued from being melted by the sun by the Fifth Doctor, who took them to the North Pole. (PROSE: Do You Smell Carrots?)

Terravores looked like mechanical mosquitoes. They had extremely limited vision. (AUDIO: The Crimes of Thomas Brewster, The Screaming Skull)

Atraxi 3 was inhabited by giant mosquitoes. (PROSE: Vampire Science)

In 3rd century Germany, robotic mosquitoes were spreading disease and killing off dozens of soldiers. They were being used by aliens to search for a cure to a plague infecting their own world. (PROSE: Silver Mosquitoes)

Jason Clearfield experimented with creating giant insects as hosts for the minds of Wyrresters. The mosquitoes he made had scopolamine in their proboscis to control the local villagers. (PROSE:The Crawling Terror)