Caterpillars are using rhythmic vibrations to communicate with ants, a newly discovered behavior that suggests a surprising level of sophistication in insect communication. The findings, published February 25 in the Annals of the Latest York Academy of Sciences, reveal that certain caterpillars mimic the vibrational signals used by ant queens to influence their colonies, potentially gaining protection or even exploiting the ants for resources.
Many caterpillars within the butterfly family are known to have close relationships with ants, a phenomenon known as myrmecophily. These relationships vary in nature, ranging from caterpillars receiving food or protection from ants to being fully integrated into the ant nest as if they were ant larvae, according to researchers.
Chiara De Gregorio, an ethologist at the University of Warwick in England, led the research team that uncovered the vibrational communication. “This raised the possibility that these caterpillars ‘might be exploiting existing communication systems within the ant colony,’” De Gregorio said. The team focused on nine caterpillar species and colonies of two ant species collected from across Northern Italy.
Using sensitive microphones, the researchers recorded and analyzed the vibrations produced by both caterpillars and ants as they traveled through the soil. The analysis focused on the tempo and regularity of these buzzing signals. “Across many animal species, rhythm is increasingly recognized as an important component of communication,” De Gregorio explained. “It’s not only what is communicated that matters, but also how.”
The study found that both caterpillars and ants produced regular, metronome-like vibrations. However, only the caterpillars most reliant on ants for survival were able to generate rhythmic patterns that matched the complexity of the ants’ signals. This included maintaining consistent pauses between pulses and alternating between long and short intervals. Researchers believe this precise rhythmic language is crucial for establishing a close partnership with the ants.
The research suggests that ants already utilize these vibrations for their own communication purposes, and caterpillars capable of mimicking them may receive increased attention and care from their ant hosts. Caterpillars sometimes supplement this mimicry with chemical signals, further enhancing their ability to integrate into ant colonies and receive benefits, such as food or protection, in exchange for sugary secretions.
Luan Dias Lima, an entomologist at the University of São Paulo in Brazil, noted the potential for similar research on metalmark butterflies, which also exhibit close relationships with ants. Comparing the vibrational communication of these two butterfly families could reveal whether a “global universal rhythm” exists for ant-butterfly interactions, according to Lima.
De Gregorio highlighted the surprising level of rhythmic complexity observed in these insect communications, particularly when compared to primates. While primates possess sophisticated brains, the ability to generate and recognize rhythm is relatively rare, found in only a few species like humans, indri lemurs, and gibbons. The caterpillar findings suggest that rhythmic communication may be more widespread among animals than previously thought.
“Observing comparable levels of rhythmic organization in ants was genuinely mind-blowing,” De Gregorio said.
