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Who knew that ants were masters of melodrama? The colonial organisms have long enchanted entomologists and animal behaviorists with their impressive physiological capabilities, unique social structures, and amazing diversity (there are more than 15,000 named ant species and subspecies). But now, two species of ants have added a macabre twist to their bag of tricks—they kill their own mothers.
Before you jump to conclusions, know that they don’t do so willingly. The matricidal ants are chemically coerced into the murderous behavior.
As researchers in Japan report in Current Biology today, the colonies of two ant species, Lasius flavus and Lasus japonicus, are invaded by two separate parasitic ant species (Lasius orientalis and Lasius umbratus, respectively) that dispatch the host colonies’ queens by manipulating host workers into attacking her. The key to influencing their victims’ behavior is a spritz of some chemical directly to the host queens. The parasitic ants get their victims’ cooperation by spraying their queen with a chemical that the workers associate with danger. Once invading queens spray hapless host queens—with what the authors of the study suggest is formic acid—the host workers dismember and kill them, their own mothers. They then accept the parasitic queen and cater to the new eggs she lays after the deceitful deed is done.
“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,” says Kyushu University biologist Keizo Takasuka, co-author of the paper, in a statement. “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.”
Though the team of researchers formally documented this fascinating interaction between parasite and host colonies for the first time, it was amateur ant enthusiasts who clued them into the behavior. Taku Shimada, who runs a well-trafficked Japanese-language blog called AntRoom, first discovered the dastardly ant dynamics between L. orientalis and L. flavus and posted about it in 2021. He is the first author on the paper. Another ant watcher, Yuji Tanaka, discovered the interaction between L. umbratus and L. japonicus, and is listed as the second author.
Read more: “Want to Get Out Alive? Follow the Ants”
The feat of manipulating workers into killing their own queens can only be accomplished after the invading colony gets past the guards. The invading parasites manage to penetrate these defenses using yet more scent deception. “Direct infiltration would fail because the workers would immediately perceive the intruder and attack her,” Takasuka noted. “To achieve this, the parasitic queen was housed with a few host workers and cocoons. After just one night, she acquired the host colony’s specific scent, providing a chemical camouflage that was essential for her to get past the initial defenses.”
It may be a dog-eat-dog world. But those who keep their eyes on the fascinating microcosms that churn beneath our feet know that it’s actually an ant-trick-other-ant-into-killing-their-own-mother world. I suppose that’s kind of a mouthful for an aphorism though. 
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Lead image: Keizo Takasuka / Kyushu University
