The pyraloid moth, a wax moth which is found worldwide, evolved an ability for localised hearing long after its basic ear structure initially developed – unlike most hearing animals, in which both developed at broadly the same time.
The study, with researchers from CNRS (Centre National de la Recherche Scientifique) in France – based at the Université François Rabelais de Tours – found that, in a type of pyraloid moth where males make mating calls, the structure of each ear gives the insects a sharp sensitivity to sound arriving from a distinct angle. It enables females to track male calls, albeit along an indirect trajectory.
The research could have potential applications in the development of microphones and other acoustic systems.
Dr James Windmill, of Strathclyde’s Department of Electronic and Electrical Engineering, led the Strathclyde research team in the study. The research paper has been published in the journal PNAS (Proceedings of the National Academy of Sciences).
He said: “In most animals which can hear, directional hearing evolved alongside basic ear structure. Pyraloid moths are different because their ears generally function as simple bat detectors with little directional ability.
“The hearing that moths evolved around 65 million years ago is a simple but highly effective way for them to avoid and escape predatory bats. However, pyraloid moths are generally smaller, are not superior flyers and have relatively high hearing thresholds. They may not detect a bat until it is close and they appear to defend themselves against bats either by diving towards the ground or by staying still and falling silent.
“Communication in moths is rare and is, in many cases, restricted to close-range courtship, where directional hearing is less of an issue, but this mechanism may have evolved in this type of moth to enable mates to be found.”
The study received funding from the European Research Council, the UK’s Defence Science and Technology Laboratory (Dstl), CNRS (Centre National de la Recherche Scientifique), Agence Nationale de la Recherche de France and Direction Générale de l’Armement.
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