Sick Ant Pupae Send a Chemical Signal Asking to Be Killed

Disease in a crowded colony is a real risk, and ants have more than one way of dealing with it. A study in Nature Communications describes one of the strangest I have come across: sick pupae that signal their own death.

The work focuses on Lasius neglectus, a small black garden ant, and comes from the Institute of Science and Technology Austria. Erika Dawson is named as lead author in the coverage, and the publication lists Sylvia Cremer. The paper is titled Altruistic disease signalling in ant colonies.

Sick worker pupae give off a chemical that prompts adult workers to destroy them. The workers remove the cocoon, bite holes in the pupa and insert poison, which acts as a disinfectant that kills both the pathogen and the pupa. In the experiments, the team extracted the odour from sick pupae and applied it to healthy brood, and the workers still destroyed the healthy pupae. A further test showed that sick pupae release the odour only when workers are nearby.

Infected queen pupae do not send the signal. The researchers suggest this may be because queens have stronger immune systems and can fight off the infection.

It is a grim strategy, but it makes sense when the colony, not the individual, is what counts. I found it a good example of why brood care in an ant nest is more complicated than simply feeding and warming the larvae.

Source: Phys.org (AFP)