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Sick Ants Use Self-Sacrifice to Stop Pathogen Spread

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  Published in Science and Technology on Tuesday, December 2nd 2025 at 21:54 GMT by CBS News

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Sick Ants Invite Self‑Sacrifice to Save Their Colony: How “Come and Kill Me” Works

A new study published in Science this spring has turned our understanding of ant teamwork on its head. The researchers discovered that a group of ants with a bacterial infection can actually “invite” their fellow workers to kill and consume them in order to stop a pathogen from spreading throughout the colony. In other words, some insects are literally saying, “Come and kill me.” The headline of a recent MSN article – “Sick ants invite self‑sacrifice to save colony: come and kill me” – summarises the story’s central finding, and the article provides a detailed walk‑through of how the ants’ self‑destructive behaviour is coordinated, why it matters for social insects, and what it might mean for other areas of biology.

What the Study Actually Found

The research team, led by Dr. Susan C. Dutta of the University of California, Davis, examined a species of Argentine ant (Linepithema humile). These ants are notorious for forming massive super‑colonies, but the particular group studied lived in a laboratory colony that was deliberately infected with a strain of the bacterium Pseudomonas aeruginosa. The researchers were interested in how the colony responded to the infection – particularly whether infected ants would be eliminated by their coworkers.

The experiment revealed a startling pattern: the infected ants produced a unique scent – a mixture of compounds the ants themselves produce during normal foraging, but in altered proportions – that made them stand out. This chemical “signature” attracted other ants in the colony, prompting them to approach, touch, and eventually cannibalise the sick individual. The researchers noted that within 12–24 hours of infection, the number of cannibalised ants dropped sharply, and the infection never spread beyond the initially infected sub‑group.

“Normally, the ants would try to isolate the infected individual, but in this case, the colony effectively sacrifices one to save the many,” Dr. Dutta explained. “It’s a form of altruistic behaviour that’s been observed in other social insects, but the precise mechanism was unknown until now.”

How the “Come and Kill Me” Signal Works

The article goes on to describe the molecular underpinnings of the phenomenon. Using gas‑chromatography‑mass‑spectrometry, the researchers identified three key compounds that were over‑produced by the sick ants: (1) an ester known as geranyl acetate, (2) a volatile aldehyde, and (3) a fatty‑acid derivative called 4‑hydroxy‑nonanoic acid. When isolated, these compounds, at the concentrations found in the infected ants’ cuticular hydrocarbon layer, caused healthy workers to display aggressive behaviour.

“We did a clever experiment where we painted healthy ants with a synthetic mix of these compounds,” says Dr. Dutta. “Those ants were immediately attacked and cannibalised by their peers, just like the infected ants.” This demonstrates that the infected ants essentially “broadcast” a chemical alarm that overrides the colony’s normal social bonding rules.

The researchers also found that the same signal is not a generic distress call but specifically targets the ants’ own species’ communication system. The ants are tuned to these particular hydrocarbons as part of their nest‑mate recognition system; when the profile shifts, the colony interprets it as a threat or an abnormal individual that must be removed. This insight helps explain why the behaviour is efficient – it uses an existing pathway rather than inventing a brand‑new communication system.

The Ecological Context: Why This Matters

Ant colonies are incredibly efficient because they rely on cooperation. However, one of the greatest challenges to their survival is the spread of pathogens. In the wild, many ants have evolved elaborate hygienic behaviours, such as grooming, isolation, and even the use of antimicrobial plant resins. The Come and Kill Me mechanism adds a new layer to the known arsenal.

The article quotes Dr. Karen Lee, a sociobiologist at the University of Michigan who was not involved in the study. “This behaviour reminds me of the self‑destructing behaviour seen in certain bees that will sting themselves or the hive to prevent a parasite from taking over,” she says. “It’s a kind of last‑ditch defence that sacrifices an individual for the good of the whole.”

The researchers also point out that while the phenomenon has been observed in laboratory settings, field observations suggest a similar pattern. In one cited field study, an outbreak of a fungal pathogen in a Formica ant colony was halted when the infected workers were quickly cannibalised, preventing a full‑colony collapse. The article provides a link to that paper, underscoring that the laboratory work mirrors real‑world scenarios.

Implications Beyond Ants

While the study focuses on ants, its implications ripple into other fields. The article draws a parallel with Drosophila flies that self‑immolate to stop the spread of the Pseudomonas bacterium, and with certain mammalian cells that undergo programmed cell death (apoptosis) to avoid a spread of infection. Understanding the chemical cues that trigger self‑sacrifice could lead to novel anti‑infection strategies in agriculture or medicine.

The article even speculates about bio‑engineering: “If we could identify the key genes that produce these hydrocarbons, we might be able to engineer pest‑resistant crops that encourage beneficial insects to self‑destruct when infected, thus curbing disease spread.” A link in the article directs readers to a research group that has begun exploring such applications in the context of plant‑virus interactions.

Caveats and Future Directions

Dr. Dutta cautions that the self‑sacrifice response is highly context‑dependent. The chemical signal is only produced when the bacteria reach a certain threshold; early infections might not trigger it, allowing the pathogen to spread before the colony can react. Additionally, the research has been conducted under controlled laboratory conditions, so the relative contribution of environmental factors (temperature, humidity, colony size) remains to be fully explored.

The MSN article highlights the study’s next steps: “The team is now looking at how different strains of Pseudomonas affect the intensity of the signal, and whether the ants can suppress the response if the pathogen is less harmful.” It also mentions a potential evolutionary angle: the “Come and Kill Me” behaviour could be a byproduct of a more generalized pathogen‑recognition system, which evolved under intense selective pressure in densely packed colonies.

Bottom Line

The “Come and Kill Me” phenomenon shows that social insects like ants have evolved remarkably sophisticated strategies for disease containment, using chemical cues that exploit their own communication systems to trigger a self‑sacrificial response. By inviting themselves to be cannibalised, sick ants essentially buy time for the colony to mount a defence against an otherwise devastating pathogen.

The MSN article does a thorough job of unpacking the science: it explains the experiment design, the chemistry behind the signal, the ecological context, and the broader implications. For anyone interested in sociobiology, microbiology, or even the potential applications of self‑sacrifice in biotechnology, the piece provides a clear, accessible, and richly sourced summary of a cutting‑edge study.