Linepithema humile, as it is scientifically called, is a small ant that originated in the Paraña delta in Argentina. With many larger ants competing in the same area, such as the giant Amazonian ants, bullet ants and fire ants, the Argentine ant needed to fight to survive.
However they did have one thing over their enemies - sheer numbers. Whereas most ant colonies only have one queen, Argentine ants have approximately one queen per 120 ants. Sometimes queens leave the home colony to find a new colony, eventually meaning mutations in their DNA.
One thing that would happen to most other ant species is that they would fight when their colonies met, as their DNA is different - not so for the Argentine ant. In the mid 19th century, when Queen Victoria was on the throne, some ants got onto 2 merchant ships that were heading to Alabama and Madeira from Argentina. The ants found themselves in a totally new environment, having found none of their methods to hunt their prey. So the Argentine ants came to form something new that none of the other ants from the Paraña delta had been able to do - combine many different colonies acting together to make one larger supercolony. By only having a few queens introduced to different places and with 90% of the queens dying each year, the chance of genetic mutation is decreased, hence letting many colonies cooperate together on a bigger scale. There are 2 colonies (the Lake Hodges colony and the Very Large colony) that have been battling for dominance around the San Francisco Bay Area for the last decade.
By the 1980s the Argentine ant had colonised most of the Earth, however by doing that they have exterminated many other species of ants and other insects, such as the Californian Carpenter Ant, which is much larger but has smaller colonies.
Recently, something new has emerged from the shadows - the Red Imported Fire Ant, a mutation of the Fire Ant from the Paraña delta, had also worked out how to form super colonies. As they were much bigger, the Argentine ants were almost totally wiped out from the south-eastern US. However this amazing species knows how to survive. As an agricultural pest, they do not care for flora or fauna - their next colony could be anywhere - in that crack in the doorframe of your bathroom or in your dog's food bowl!