# Rhythmic Signaling of Ants and Butterflies With Varying Degrees of Myrmecophily

## TL;DR

Butterflies that closely interact with ants share complex rhythmic signals with ants, suggesting evolution for mutualistic communication.

## Contribution

First study to investigate rhythmic structure of vibroacoustic signals in myrmecophilous butterflies and ants.

## Key findings

- Highly myrmecophilous butterflies and ants share complex rhythmic patterns like isochrony and double meter.
- Species with weaker ant associations show simpler or irregular rhythms.
- Rhythmic complexity may enhance signal recognition while balancing energy and detection risks.

## Abstract

Myrmecophilous organisms have evolved in several arthropod lineages, developing specialized traits to communicate with ants. In butterflies, these include morphological, visual, chemical, behavioral, and acoustic adaptations. While acoustic communication has long been overlooked, recent studies show that vibrational signals mediate key aspects of caterpillar–ant interactions. Yet, no study has specifically investigated the rhythmic structure of such signals in myrmecophilous contexts, despite growing evidence that rhythm is a fundamental component of signal architecture across taxa. We examine the rhythmic properties of vibroacoustic signals from two ant and nine butterfly species differing in myrmecophily degree. We tested whether rhythmic features such as pulse train tempo, intertrain interval, and rhythmic patterns vary across taxa and reflect the strength of their ecological association with ants. Our results reveal that ants and highly myrmecophilous species share a complex rhythmic organization (isochrony and double meter), likely reflecting convergent adaptation to tight mutualistic interactions. Species with intermediate or no myrmecophily associations showed more variable or simplified rhythms. Temporal regularity and precision could possibly balance the need for signal recognizability with energetic constraints and avoidance of detection by unintended receivers. These findings highlight the role of temporal patterning in vibroacoustic communication, influencing signal efficiency and recognition in ant–butterfly interactions.

Myrmecophilous butterflies evolved diverse adaptations to communicate with ants, including acoustic ones. We analyzed the rhythmic properties of vibroacoustic signals in two ant and nine butterfly species differing in myrmecophily. Highly myrmecophilous species and ants shared complex rhythmic structures (isochrony, double meter), suggesting convergent evolution for mutualistic coordination. Species with weaker associations showed simpler or irregular rhythms, highlighting rhythm's key role in signal efficiency and recognition.