A screenshot of the paper published on the Proceedings of the National Academy of Sciences of the US

Research on Jurassic-era fossil katydids from Ningcheng County, North China's Inner Mongolia Autonomous Region, has provided the first evidence that insects capable of ultrasonic communication existed 165 million years ago, during the Middle Jurassic, a researcher at the Capital Normal University (CNU) told the Global Times on Thursday.

The study has provided the first clear evidence that the evolutionary origins of ultrasonic communication in insects predated the emergence of bats, placing them more than 100 million years earlier than the bats of the Eocene epoch.

The academic community had long believed that ultrasonic communication in insects evolved as an adaptation to predation by bats.

The findings, were published online in the Proceedings of the National Academy of Sciences of the US on Wednesday. The research was conducted by the CNU in collaboration with multiple research teams in China and abroad. 
 
"The study allows us to hear insect calls from the Jurassic period across 165 million years, proposes a new theory of two-way acoustic selection between insects and mammals in the Mesozoic Era, and provides a more complete picture of the co-evolution of hearing and sound production in terrestrial animals," said Ren Dong, co-author of the paper and professor at the CNU.

Researchers selected 20 forewing specimens from nine species of male katydids in the Yanliao Biota of the Daohugou area in Ningcheng County and compared them with a relict katydid group, which is now found only in Southwest China's Sichuan Province. They developed a paleoauditory reconstruction process involving fossil wing morphology, wing resonance simulation, syllable reconstruction and calling-song temporal prediction to reconstruct the full acoustic characteristics of the calls produced by these ancient insects.

The calling frequencies of the nine fossil katydid species ranged from 5 to 20.5 kilohertz (kHz). Five species produced low-frequency pure tones in the 5-7 kHz range, while the remaining four occupied the medium- to high-frequency range of 8-20.5 kHz. The carrier frequency of one fossil species reached as high as 20.5 kHz, confirming that insects capable of true ultrasonic communication already existed during the Middle Jurassic.