Do you want to hear what the insects in a Jurassic forest in Mongolia sounded like?
Obviously, there were no recording devices, let alone humans, 165 million years ago, but there were katydids, insects in the order Orthoptera that are known for their sound-making abilities. And for a new study, paleontologists have recreated katydid melodies of the time by examining the katydid’s delicate file and plectrum structure via fossils.
Take a listen:
The file consists of a serrated hard strip on the underside of the left forewing that gets scraped by a plectrum on the edge of the right forewing. A drum-like cell further resonates the vibrations from the scraping and amplifies the sound. There are also sets of teeth on the plectra spaced at different intervals (closely spaced teeth yield high frequencies, while wider spacing makes for lower frequencies). Amplitude can be varied by the amount of pressure exerted from the file on the plectrum.
In a Jurassic forest, katydids had no competition for airspace from squeaking bats, as bats didn’t evolve for another million years. Not that it would have mattered anyway; even early on, katydids had specialized ears to pick up each other’s calls—located on their front legs just below the knees, but similar in three-part structure to those of mammals. Sound travels into the outer ears, through the middle ears, and to the inner ears where a tiny sensory organ detects the sound vibrations.
The study authors also hypothesize that “the ability to produce sound by wing stridulation could have appeared before hearing as a defensive tool to deter terrestrial predators.” Although there were no bats, there were plenty of insectivorous mammals and reptiles, such as tree-climbing theropods and flying pterosaurs, in the Jurassic forests of China, which perhaps would be repelled by the squeaky-blackboard sounds.
If nothing else, katydids of the era certainly knew how to make sure that their voices were heard. 
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Lead Image: Lkunl / Adobe Stock
Video Credit: Jun-Jie Gu, Fernando Montealegre-Z, Thorin Jonsson, and Dong Ren
