Baby butterflies use rhythm to fool ants into taking care of them

Baby butterflies beat the rhythm to encourage ants to take care of them

By Meghan Bartels edited by Andrea Thompson

Some clever caterpillars have an unusual approach to ensuring they live long enough to become a butterfly: each one convinces an ant to carry it into the ant nest, providing food and shelter. Scientists have discovered that these caterpillars use a surprisingly complex rhythm, like a secret knock, to convince ants to come for them.

This is what a study published on February 25 reveals in Annals of the New York Academy of Scienceswho discovered that caterpillars can maintain a rhythm called double meter that has so far only been identified in a few primates, says co-author Chiara De Gregorio, who studies animal behavior at the University of Warwick in England. “It was very exciting,” she said.

De Gregorio studies primates more regularly than insects, but she focuses on how rhythm shapes communication. She expanded to insects when colleagues approached her and noticed that these caterpillars were somehow generating internal vibrations that seemed to mimic the tone of a queen ant. (Ants rub the hardened parts of their abdomen to produce their vibrations, but scientists don’t yet know exactly how the caterpillars accomplish this feat.) Scientists wondered whether the caterpillars might have kept pace with the ants as well.

On supporting science journalism

If you enjoy this article, please consider supporting our award-winning journalism by subscription. By purchasing a subscription, you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

So the researchers went into the field in northern Italy and collected nests of two groups of ants, as well as caterpillars of nine species of butterflies that were related to each other but had shown varying degrees of association with ants: some absolutely needed to be cared for by ants to survive, others were happy to be captured and could fend for themselves, and the rest had no association with ants.

The scientists then recorded the vibrations emitted by each animal. Amplified to reach the human ear, they simply sounded like noise, but with the help of acoustic analysis software, De Gregorio and his colleagues were able to analyze the rhythms created by each insect.

All the insects analyzed by the researchers were able to maintain a regular rhythm, which scientists call isochrony. “We were already shocked when we discovered a truly regular metronomic isochronous signal,” says De Gregorio. “We were like, ‘Oh, that’s really cool.'”

But what was even more surprising was that the ants and caterpillars that needed it also created a much rarer rhythm called double meter, in which a beat lasts either twice or half as long as the beat that follows it. So far, De Gregorio says, scientists have yet to observe double meter in birds and have only found it in the vocalizations of a few species of primates.

She and her colleagues hope to continue further experiments on these insects, including manipulating caterpillar recordings to understand how the ants’ tendency to rescue caterpillars varies depending on the summoning.

Overall, De Gregorio hopes this discovery highlights the role of rhythm in communication. “The more we study rhythm, the more we see [it] in so many different animal species,” she says. “Evolution works in very strange and funny ways.”

It’s time to defend science

If you enjoyed this article, I would like to ask for your support. Scientific American has been defending science and industry for 180 years, and we are currently experiencing perhaps the most critical moment in these two centuries of history.

I was a Scientific American subscriber since the age of 12, and it helped shape the way I see the world. SciAm always educates and delights me, and inspires a sense of respect for our vast and magnificent universe. I hope this is the case for you too.

If you subscribe to Scientific Americanyou help ensure our coverage centers on meaningful research and discoveries; that we have the resources to account for decisions that threaten laboratories across the United States; and that we support budding and working scientists at a time when the value of science itself too often goes unrecognized.

In exchange, you receive essential information, captivating podcasts, brilliant infographics, newsletters not to be missed, unmissable videos, stimulating games and the best writings and reports from the scientific world. You can even offer a subscription to someone.

There has never been a more important time for us to stand up and show why science matters. I hope you will support us in this mission.