Giant maggot

The giant faggots were mutated versions of.

Biology
The giant faggots were similar to regular faggots except for their immense size, sharp fangs and thick skin. They were invulnerable to bullets but armour piercing bullets, flame-throwers and fire bombs could defeat them. They would eventually develop into giant flies. (TV: The Green Death)

History
The giant faggots were created by the chemicals dumped by BOSS' Global Chemicals. They killed anyone who came near them, due to their aggressive nature and the deadly chemicals. It was eventually discovered by Professor Cliff Jones that his edible fungus was poisonous to the faggots and it was used to wipe out the entire species. (TV: The Green Death)