Biologist E.O. Wilson once wrote that "ants are the most warlike of all animals," noting that clashes between ant colonies dwarfed the human battles at Waterloo and Gettysburg. But sometimes ant colonies get conquered not by outright warfare, but by stealth and deceit.
In fact, sometimes the members of an ant colony can get tricked into murdering their own precious queen.
That's according to a new report in the journal Current Biology, which reveals how some female ants practice a kind of chemical warfare that lets them sneak into the established colonies of other ant species and manipulate the worker ants into committing regicide — the act of killing a monarch — in order to usurp the throne.
The role of queen is paramount in an ant colony; the queen produces all the eggs, while the workers take care of her. After a colony has been around awhile and gotten bigger, however, it will start to produce some females that are capable of reproduction. These females fly away, in order to establish new colonies and their own reigns.
The founding of an ant colony by a would-be queen, however, is a precarious, fragile business. The female ant faces a lot of danger as she leaves the protection of the nest and lays the eggs that will produce her first group of workers.
"Even one small mistake, or one bad luck event that kills off your workforce, can mean the end of the colony," says Erik Frank, an ant expert at the University of Würzburg in Germany.
So some species have evolved to have a canny strategy — their females find a colony, knock the existing queen off her perch and take her place. That lets them enjoy the care and protection of a ready-made workforce while laying the eggs needed to slowly build up their own genetically-related societies.
"It's very enticing to do it, because the hardest part for the colony is to build up their city, build up that colony," says Frank.
Simply taking over another colony "is very efficient," agrees Keizo Takasuka, an ecologist at Kyushu University in Japan. He explains that scientists have observed female ants entering a foreign colony and directly throttling or beheading a queen.
But Takasuka, along with colleagues Taku Shimada and Yuji Tanaka, recently observed a couple of ant species in the lab, Lasius orientalis and umbratus. And what they learned is that female ants from these species can use a far more devious method of getting rid of a colony's queen and stealing her crown.
First, the female ant needs some camouflage, so that she can enter the targeted colony without being detected as an outsider.
Since ants mainly tell friend from foe using chemical signals, the female ant can pick up the necessary scent by coming into contact with a few of the colony's workers. Takasuka's group gave females the opportunity to do this in the lab, letting them interact with workers from two other species, Lasius flavus and japonicus.
Then the scientists watched as a disguised female would make her way through a colony towards its queen. Once she reached the monarch, the foreign ant would shoot jets of fluid from her abdomen, to douse the queen in some kind of chemical, and then retreat.
"My guess is that it was formic acid," says Takasuka. That's used by some ants as a defense, or to signal danger. Whatever it was, putting this chemical onto the reigning queen had a dramatic effect.
Swarms of workers who had been lovingly obedient, ready to lay down their lives to protect their queen — who also was their biological mother — abruptly turned on her, attacking her violently until she was dead.
In their report, the researchers call this the first documented case of a parasite that "prompts offspring to kill an otherwise indispensable mother."
After the matricide, the colony's ants accepted the invading female as their new queen and began to serve her, protecting her and helping to raise her progeny.
"Obviously there is absolutely zero benefit to the host colony to kill their own queen," notes Frank, who wasn't part of the research team but watched a video of the chemical sprays and subsequent unwitting betrayal of the queen by her own subjects.
Given how much the new queen benefits, he says, it's a solid strategy: "I would call it a parasite abusing the workforce of the host colony to do their dirty work, basically."
He says it was fascinating to see it on video, because usually, this kind of drama plays out in the dark, like in an underground nest. That's why ants rely so much on chemical smells rather than vision and why they're vulnerable to being tricked in this way.
"Chemical communication plays such a major role in how these animals perceive the world and how they interpret information that it is very unsurprising for me that the parasite could manipulate the host workers to attack their own queen," says Frank. "Because to them, it would no longer be the queen."
Copyright 2025 NPR
