Caterpillars adjust the rhythm of their vibrations to communicate with ants.

Butterfly caterpillars modulate the rhythm of their vibrations to communicate with ants and enhance integration within colonies. Species with a greater dependence on ants reproduce complex rhythmic patterns similar to those of their hosts. The adjustment includes isochronous pulses and a double-mesh pattern.

Researchers from the University of Warwick, the University of Turin, and the Forest Research Institute analyzed vibroacoustic signals from two ant species and nine butterfly species from the Lycaenidae family. The recordings included species with varying levels of myrmecophily (symbiotic and mutualistic association between ants and other organisms).

Vibrations that propagate

Caterpillars produce vibrations that propagate through the soil, plants, or nest walls. Ants use vibrations to coordinate alarm, defense, and social organization. The study evaluated pulse timing, intervals between sequences, and rhythmic structure.

The results indicate that all species analyzed use an isochronous pattern (phenomena that occur at equal time intervals). This pattern maintains regularly spaced pulses. However, only ants and caterpillars with high myrmecophily exhibited a double rhythm, characterized by alternating long and short intervals.

The most dependent caterpillars replicated two central characteristics of the ants: isochrony and double time signature. The study identified temporal convergence between these groups. Species with intermediate or weak association exhibited simpler or more variable rhythms.

Four categories

The study grouped the butterflies into four categories: non-myrmecophily, low, medium, and high. Species with a high degree of myrmecophily, such as Phengaris alcon e Plebejus argusThey shared a rhythmic organization more closely resembling that of ants than species with weak or nonexistent associations.

In addition to rhythmic structure, the study measured the regularity of the signals. Caterpillars with high myrmecophily showed greater precision in the isochronous pattern than the ants themselves. The result suggests fine-tuning of the signal to facilitate recognition within the nest.

Highly dependent caterpillars also exhibited longer intervals between pulse sequences compared to ants. The authors associate this pattern with possible energy savings or reduced detection by unwanted organisms.

Intermediate level

Species with an intermediate degree maintained an isochronous rhythm, but with a slower pulse time. These groups interact with multiple ant species. The pattern suggests a more generalist signal.

Species with low or no myrmecophily exhibited similar temporal characteristics. The rhythm maintained a simple structure. The study indicates that rhythmic modulation intensifies as the level of ecological integration with ants increases.

The authors indicate that the temporal organization of signals enhances communication efficiency in subterranean environments, where vibrations compete with constant noise. This work expands the understanding of interspecific communication and suggests that rhythm is a central component in the interaction between caterpillars and ants.

More information at doi.org/10.1111/nyas.70223