Parasitic Ant Queens Use Chemical Trickery To Make Workers Kill Their Own Mother, Study Confirms

A new study has uncovered an ant takeover strategy so extreme it seems ripped from science fiction: parasitic queens that trick a host colonys workers into murdering their own queen so they can claim the throne themselves.

The research, published in Current Biology and led by Assistant Professor Keizo Takasuka of Kyushu University, documents how parasitic ant queens weaponize chemical signals to infiltrate a nest, incite chaos, and trigger the host colony to execute its ruling queen — their mother. The work traces back to observations by longtime ant enthusiasts who recorded the behavior years before it was formally studied.

“The initial discovery was made by my friend Taku Shimada, the first author of the paper, who has been passionate about ants since childhood and runs a popular blog called AntRoom. He observed the colony infiltration and posted about it in 2021,” Takasuka said. “I found the post three years later and was so astonished. I thought it was a very valuable discovery that deserved to be documented as academic knowledge.”

The team examined two different parasitic species within the genus Lasius: Lasius orientalis, which infiltrates the nests of Lasius flavus; and Lasius umbratus, which infiltrates the nests of Lasius japonicus. The takeovers unfold with ruthless precision.

In one case, a Lasius orientalis queen repeatedly sprayed the resident queen about 15 times over 20 hours, gradually agitating the workers. Within four days, the workers turned on their mother, mutilating and killing her. In another, a Lasius umbratus queen required only two sprays to provoke an immediate and fatal attack; the host workers swiftly dismembered their queen.

“The parasitic behavior of the latter species of ants was discovered by Yuji Tanaka, who is the second author of this study. He is another enthusiastic amateur of ants and followed the same observational methods established by Shimada,” Takasuka said.

Researchers believe the sprayed substance is formic acid, a defensive chemical widely used across ant species. In these confrontations, it appears to function as a deceptive alarm cue.

“In both cases, the host and parasite belong to the same genus, so they both have formic acid and recognize it as a danger signal,” Takasuka said. “We believe that when their queen is suddenly covered in a large amount of this chemical, the workers perceive their own mother as a colony-threatening crisis which triggers their aggressive defensive behavior.”

The parasitic queens success depends first on slipping past the nests guards. To do that, she must steal the colonys scent.

“Ants live in the world of odors,” Takasuka said. “Before infiltrating the nest, the parasitic queen stealthily acquires the colonys odor on her body from workers walking outside so that she is not recognized as the enemy.” In their controlled experiments, the researchers replicated this step by housing the invader with host workers and cocoons.

“Direct infiltration would fail because the workers would immediately perceive the intruder and attack her,” Takasuka said. After a single night of exposure, the parasitic queen had chemically camouflaged herself well enough to enter unnoticed. Once she attacks the resident queen, however, she must immediately retreat.

“She knows the odor of formic acid is very dangerous, because if host workers perceive the odor they would immediately attack her as well,” Takasuka said. Only after the host workers complete the killing does the parasitic queen return to assume power and begin laying eggs. The workers then tend to her brood as if she were their rightful queen.

Although the two parasitic species studied are not close relatives, they share the same genus, which has two known origins of social parasitism. Takasuka described the similarity in takeover strategies as convergent evolution.

“My own research focuses on how parasitoid wasps manipulate the behavior of spiders, so I know that in the natural world, parasitic organisms utilize many various and interesting strategies to infect their hosts,” he said. “This discovery in ants is another fascinating example. I am interested in investigating these different host-killing strategies to understand the evolutionary pressures that drive them.”

The study also delivered one unexpected revelation about the human imagination. When Takasuka searched for mythical or literary parallels to matricide by deception, he came up empty.

“At first, I wanted the title of this study to exemplify a fable where a daughter is tricked to kill their mother. I asked CHATGPT if this kind of matricide appears in a fictional story, but it said no such story exists,” Takasuka said. “So, this is an example of nature going beyond what weve seen in fiction.”