FunNature & AnimalThis is the eerie sound of the chemical defenses...

This is the eerie sound of the chemical defenses of insects

The larvae of the Craesus septentrionalis fly protect themselves from predators, especially ants, by secreting cocktails of repellent chemicals. One of the most common methods to evaluate the effectiveness of these defenses consists of carrying out bioassays with predators and prey. But a team of researchers has published a paper with a very different approach, which has consisted of translating the chemical composition of signals into sounds and then measuring the reaction of humans.

The sounds obtained are eerie and could well serve as a soundtrack in a horror movie. To assess its effect, the researchers recruited 50 volunteers, and measured the distance they walked away from the speakers when they heard the terrifying sound. ” Curiously, the responses of humans and ants were correlated, indicating that this ‘sonification’ technique is effective in approaching the world of predator-prey interactions “, explains Jean- Luc Boevé.

Sonification

This researcher began to think about the possibility of transforming volatile chemicals into sounds in 2009. “For example, there are small molecules such as acetic acid contained in vinegar or pungent formic acid emitted by some ants that are very volatile and diffuse in the air quickly “, he explains” I thought it would be possible to translate high or low volatility in high or low tones, as well as other chemical characters in different sound traits “.

Chemicals are transformed into sounds through a process called sonification. The most important characteristics of each molecule, such as its molecular weight and the functional groups it has, are assigned to different sound parameters, such as pitch, duration, and timbre. The chemical information is fed into a synthesizer that produces a sound for each molecule, and these sounds are then mixed at various volume levels to build a sound for the defensive secretion of each species of insect.

This study takes advantage of the fact that our brain processes information differently depending on the sense we use to perceive it. “Typically, a sonification process is used to detect particular phenomena in large data sets”, Rudi Giot, computer engineer at the Higher Industrial Institute in Brussels. “Examples of such phenomena are earthquakes in seismological data or network piracy in the transmission of data over the internet.”

This project required years of laying the groundwork and completing other more classical experiments, including chemical and morphological analyzes of insects. The researchers, who have published their work in the journal Patterns, hope that their method will be complementary to already existing techniques for testing volatile compounds, especially in cases where the seasonal availability of an insect is unfavorable or when collecting quantities large enough of their secretion is a challenge.

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