‘Bad-smell’ ants trick other species into killing their own mother in dramatic display of matricide in nature

Video shows parasitic ant queens tricking workers into killing their mothers (Current Biology / Takauka et al.)

Dramatic death scenes involving daughters tricked into killing their own mothers is “an example of nature going beyond what we’ve seen in fiction,” according to just-published entomology research.

What played out in front of researchers was so unusual that when lead author Keizo Takasuka looked for similar stories of matricide, her search came up short.

The scientist at Japan’s Kyushu University said in a news release about this research that artificial intelligence assistant ChatGPT told her “no such story exists.”

What she and other researchers witnessed was a new form of host manipulation, as described by the team behind the study published in Cell Press journal Current Biology Monday. This term refers to when an invading parasitic species tries to increase its own chances of survival by doing something to change its host.

In this case, a parasitic ant queen invaded an existing colony, then sprayed the existing queen with a foul-smelling fluid that signalled to her daughters to attack. The parasitic queen was then able to take over, with the worker ants in the colony serving her instead.

Researchers saw this happen with perpetrators of the Lasius orientalis and Lasius umbratus varieties, species commonly known in Japan as “bad-smell ants” because they are able to spray a foul-smelling chemical. It is presumed this chemical is formic acid, and that it is stored in a specialized organ, the team said in a news release.

These species are described in the research as “so-called ‘social parasites’ that execute a covert operation to infiltrate and eventually take over.” The fallen queens in this case were Lasius flavus and Lasius japonicus.

Using odour to their advantage

The schemes of the parasitic queens involve several steps.

“Ants live in the world of odours,” Takasuka said in the news release outlining this violent usurp. “Before infiltrating the nest, the parasitic queen stealthily acquires the colony’s odour on her body from workers walking outside so that she is not recognized as the enemy.”

These parasitic ants take advantage of the importance of smell again when they spray the queen. This disguises her normal scent with something “repugnant,” and prompts the daughters’ attack, Takasuka said.

The parasitic queens then, briefly, leave the crime scene, seemingly aware that the daughters could sense the odour on them and attack, according to Takasuka. But they’ll come back and spray the queen again until she’s dead, if needed.

Then the usurpers will take the place of the queen and lay their own eggs, with the worker ants who’ve killed their mother taking care of these new queens and their offspring.

What’s new about this research?

While social parasitism is a known technique – ants have been known to infiltrate and directly kill the queen – the study published Monday details what researchers say is the first time this matricidal aftermath has been observed by scientists.

Matricide is rarely seen in nature, researchers said, and while it may seem maladaptive, previously observed instances have shown advantages for the nourishment and survival of the younger generations. For example, offspring might eat their parents, or removal of the parents might allow the next generation to thrive as there is less competition for food.

But in this case, they said, it seems that no one really profits except for the parasitic queen.

So far, use of formic acid to incite violence has only been witnessed in ants in the formicinae subfamily, Takasuka said, “but I don’t rule out the possibility that non-formic-acidic ants and social wasps commit matricide in similar ways.”