Scientists have confirmed a never-before-seen type of insect behavior. In a study published in the journal Current Biology, behavioral ecologists at Japan’s Kyushu University describe two species of ants that engage in matricide, killing a colony’s queen. But the spark that ignites the uprising isn’t generated from within. According to researchers, the queen’s downfall begins with chemical coercion instigated by outside, parasite ant agitators.
The insect and arachnid worlds are full of examples of males getting a raw deal. Numerous female spiders promptly devour their partners after mating, while praying mantises are famous for similar snacks. The evolutionary rationale is sound, if unsentimental. After performing his reproductive duties, males are simply more useful as a food source than a parent. The inverse reasoning explains why matricidal incidents are far rarer–the genetic survival odds improve when there are more females around to birth multiple generations of offspring.
“Up until now, only two types of matricide have been recorded in which either the mother or offspring benefit,” study coauthor Keizo Takasuka explained in an accompanying statement. In this case, Takasuka and colleagues observed an entirely new type of matricide, one in which “neither [mother or offspring] benefit; only the parasitic third party.”
Commonly known as “bad-smell ants” in Japan, the species Lasius orientalis and umbratus are examples of social parasites. Both respectively target colonies of Lasius flavus and japonicus ants for their stealthy overthrow plots. The usurping begins when a would-be queen sneakily acquires a colony’s worker ant scent by interacting with them as they forage outside. They then infiltrate the home and head for the true queen. Once locating her, the parasitic ant sprays her with a foul-smelling chemical.
“Ants live in the world of odors,” said Takasuka. “The parasitic ants exploit that ability to recognize odors, we believe, by spraying formic acid to disguise the queen’s normal scent with a repugnant one. This causes the daughters, who normally protected their queen mother, to attack her as an enemy.”
During the original queen’s downfall, the parasitic ant will even retreat and hide as the workers kill their leader. In some instances, she’ll return multiple times to continue tossing formic acid on the original queen to ensure her murder.
“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.
After the target is assassinated and removed, the parasitic ant queen assumes the throne and begins laying her own eggs. From there, the host colony’s workers will even begin taking care of her and her offspring.
Ecologists have previously reported this social parasitic behavior to exist, but Takasuka’s team is the first to capture the entire revolution on video. Although the researchers have finally confirmed the first ants of their kind, they doubt L. orientalis and umbratus are alone in their subversive behaviors.
“Only ants in the subfamily Formicinae use formic acid to elicit violent responses, but I don’t rule out the possibility that non-formic-acidic ants and social wasps commit matricide in similar ways,” said Takasuka.
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