A frequency of 130 kilohertz. Difficult to obtain simply by rubbing one's wings against each other. So Fernando Montealegre and Glenn Morris of the University of Toronto have begun to study the male specimens of Arachnoscelis, a grasshopper that lives in the tropical forests of Colombia, capable of producing ultrasound with that frequency.

Observing them by electron microscope, the two researchers discovered that the rubbing produces ultrasound due to the particular position of the legs. "Taking advantage of the elastic energy - said Montealegre - the animal can therefore save metabolic energy, since it does not have to contract its muscles very much".

In the photo: the Colombian rainforest inhabited by ultrasonic grasshoppers.