PRAWNS

The prawns are an arthropod-like extraterrestrial species of unknown origin who developped advanced technology and space faring capacities. A ship containing a leaderless group of one million individuals came ot Earth in the first decenny of the 21st century. It became stranded over Johannesburg, South Africa after a command module separated from the ship and dropped to Earth, nowhere to be found.

Note: Prawn is not the species real name, but the surname given to them by the humans as their real name remains unknown.
Source: Neil Blomkamp, Teri Tatchell, District Nine.