M is for... Maggots

When Global Chemicals began secretly pumping industrial waste into the abandoned mine workings in the Welsh village of Llanfairfach, the highly toxic substance caused a mutation in some of the local wildlife. 

Common or garden maggots grew to enormous size after consuming the waste. Their bite injected the toxin into the blood stream, causing the flesh of their victims to turn bright green as they died.

As soon as the first miner's body was discovered - that of a man who was carrying out one of the annual checks of the mine - UNIT were called in. However, their main role was to protect the chemical company from the demonstrations waged against it by ecologist Professor Clifford Jones, who ran a commune in the village. 

The Doctor found out about the giant maggots when he ventured into the mine to rescue Jo Grant, who had gone down to help another stricken miner. He brought an egg out with him to study. This later hatched at the commune and killed the henchman of Global's CEO, Dr Stevens, who had come to steal it as part of the company's cover-up.

This maggot was later found dead after consuming a meat substitute developed by Prof. Jones. The Brigadier, under pressure from Stevens and his powerful government supporters, had blown up the mine, but this had merely resulted in the maggots breaking out onto the surface all over the area.

The meat substitute was found to be able to destroy them, as well as providing an antidote to those infected with their toxin.

Sergeant Benton discovered an empty chrysalis. The Doctor realised that the insect which had emerged would be a giant fly, capable of spreading the "Green Death" all over the country. He and Benton were attacked by the creature as they went about poisoning the maggots. The Doctor threw his cape over it as it flew past, breaking its neck and killing it. The other maggots were destroyed before they could pupate.

Appearances: The Green Death (1973).

• The maggots were realised in a number of ways, including rod puppets when interacting with actors, and using real ones on model landscapes. According to the VFX team, inflated condoms were also used, though the director claimed they were party balloons.
• The script gave them a "thick chitinous skin". Jon Pertwee pronounced "chitinous" with a soft "ch" - as in church. A viewer wrote in to the production office with the short poem "The reason I'm writin' / is how to say kitin".