CALAMARI FLY

The Calamari fly is an omnivorous nomadic animal species that lives in swarm. The swarm's path seems random and based on external olfactory inputs for what specialists have been able to determine. An adult fly can come up to a lenght of about 30 centimeters.

MIDOMAR

An 5th cm high alien species whose members can travel through radio waves and can recorporate themselves by draining energy from radio receiver devices.
Source: Torchwood website

ARKANS

Almost liquid alien species which developed a space fairing civilisation who visited the solar system in the early 21th century. They cannot survive in an Earht type envrionment.
Source: Torchwood, "Cyberwoman"