Singing insect relatives of modern katydids broadcast ultrasonic mating calls in forest habitats during the Middle Jurassic period. Scientists long assumed that insects developed ultrasonic songs only after echolocating bats emerged as aerial predators millions of years later during the Eocene epoch. Instead, ancient ensiferan insects generated ultrasound by rubbing specialized tooth-lined wing files against rigid scrapers to vibrate their stiff forewing cuticle.
Sound production begins when an insect draws a rigid plectrum on one forewing across a microscopic row of ridges on the other forewing. This physical motion works like running a stiff guitar pick across the fine teeth of a comb. Each rapid strike flexes the hardened wing membrane, launching pure-tone acoustic waves into the forest air to avoid location by predators. Specialized file structures and varying wing sizes allowed different insect species to produce distinct sound pitches and acoustic patterns.
Researchers studied twenty ensiferan fossils representing nine distinct species preserved in rock from the Jiulongshan Formation in Inner Mongolia, China. The team integrated anatomical wing measurements, biomechanical simulations, and evolutionary relationships to calculate the original vibration frequencies of each wing. While most preserved species sang at low frequencies, one ancient insect broadcast pure ultrasonic tones exceeding twenty kilohertz.
These fossil wing reconstructions allow researchers to map ancient forest acoustics and analyze how early animal hearing systems evolved together. The reconstructed sound frequencies indicate that hearing abilities in early predatory mammals drove the diversification of Jurassic insect songs long before echolocating bats existed.