Macra

Home Planet: Unknown, but these lived on New Earth
Life Form: Crustacoid
Episodes: Gridlock

The Macra were a crustacoid race that survived on unclean and poisonous gases, to humans, but the Macra consumed all they wanted. In New Earth, they hid under the New New York motorway, which was gridlocked at that time, in all the fumes given off by the (flying) cars, which made it really foggy, as it was all underground with no ventilation. A colony of Macra had escaped from New New York Zoo and made their way to the motorway. Like they normally did, they fed off the poisonous gases, and occasionally on a stray car on the ‘Fast Lane’, which wanted a faster route. These Macra had gigantic claws, which they could use to grab whole cars. They had glowing eyes, on the top of stalks, protruding from their heads, and had six, thin legs. They used movement to hunt, and didn’t show much sign of intelligence when the Tenth Doctor encountered them. They were defeated when the Doctor, aided by the face of Boe, who gave his life, opened up all the trapped people on the motorway, and all the fumes, their food, escaped.