15 million dead in six months: The war no one has heard of

A study from the University of California, San Diego estimates that at least 15 million worker ants have died in battles between Argentine ant supercolonies in Southern California over six months. The ants, originally from South America, spread worldwide through maritime trade in the 19th century. Due to low genetic diversity, separate colonies began cooperating and formed vast supercolonies spanning hundreds of kilometers. When ants from different supercolonies meet, they recognize each other as enemies and break into battles. Researchers tracked 16 border points between rival colonies in the San Diego area and found that in about 40% of weekly visits, they encountered battles that resulted in an average of about 15,000 dead ants per clash. Despite the massive killing, neither side managed to win the war, and the border lines remained almost unchanged. Biologist Mark Moffett noted that in Argentine ants, the 'dear enemy effect' that reduces aggression over time is almost absent. The article notes that a 2025 study confirmed the ants are still widespread in the area but did not examine the war between colonies.