Imitating the rhythmic chatter of an ant prompts workers to protect or even feed the caterpillar
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Some caterpillars speak by swaying to the rhythm of the ants.
By shaking like a cell phone receiving a call while in vibrate mode, the caterpillars Cuddle with the ants and reap benefits for both of them. The results, published on February 25 in the Annals of the New York Academy of Sciencessuggest that the ability to keep the rhythm may be more widespread in the animal kingdom than researchers previously thought.
Many caterpillars in the thin-winged butterfly family are “myrmecophilous” or ant-loving. These larvae have developed close relationships with ants, including pavement ants, of the genus Tetramoriumand those like Myrmica. The degree and type of relationship varies. Some caterpillars receive food or protection from ants; others are fully considered a brood of ants and adopted into the nest. These caterpillars can then exploit the nest by feeding on ant larvae.
Caterpillars sometimes mimic the chemical signals of ants to befriend them, rewarding their hosts with sweet excretions. But research has suggested that some caterpillars copy the way ant queens vibrate to communicate with their colony, says Chiara De Gregorio, an ethologist at the University of Warwick in England.
This raises the possibility that these caterpillars “could exploit existing communication systems within the ant colony,” says De Gregorio.
She and her colleagues collected nine species of caterpillars and colonies of two species of ants in northern Italy. The researchers classified the caterpillars as ranging from unrelated to ants to highly myrmecophilic – a parasite completely dependent on ants for survival.
Using sensitive microphones, the team recorded and analyzed the tiny vibrations emitted by caterpillars and ants as they traveled through materials such as soil. This allowed close examination of the tempo and regularity of the buzzing signals.
“In many animal species, rhythm is increasingly recognized as an important element of communication,” says De Gregorio. “It’s not just what is communicated that matters, but also how.”
The caterpillars and ants vibrated in a regular rhythm, much like the ticking of a metronome, she said. But only the caterpillars most dependent on ants could produce rhythmic patterns matching the ants’ complexity, including keeping regular pauses between pulses and alternating long and short spaces. This precise rhythmic language may be important in forming a close partnership with ants.
De Gregorio believes that ants were already using these vibrations for their own communication needs. Caterpillars that could exploit this system “would receive more attention and care from the ants,” she says.
Luan Dias Lima, an entomologist at the University of São Paulo in Brazil, wants to see a similar study on metalmark butterflies. Their caterpillars have independently evolved close relationships with ants, so comparing the two butterfly families could reveal whether there is an “overall universal rhythm” to ant-butterfly communications.
De Gregorio says the degree of rhythmic complexity of this communication between insects particularly fascinates her, especially as a student of primates. Primates have very sophisticated brains, but rhythm generation and recognition is still rare among them, only found in a handful of species like humansindri lemurs and gibbons. The findings about butterflies could mean that keeping a rhythm could be something fundamental to communication and more widespread among animals than previously thought.
“Observing comparable levels of rhythmic organization in ants was truly mind-blowing,” she says.