In the last 150 years, the only known specimen of a species of grasshopper-like insect known as Prophalangopsis obscura sat quietly in the London Natural History Museum, but now some scientists have determined what it would have looked like.
A British/Austrian team used very sophisticated equipment and an understanding of the physics of insect acoustics to determine what this species would sound like when singing for a mate, providing insight into the ancient insect soundscape of the Jurassic period.
Katydids are grasshoppers and crickets.
This holotype, or single known specimen, is one of eight remaining species of the approximately 90 that were abundant during the Jurassic period.
The research team showed that the sounds produced by this particular insect would have been similar to, though distinguishable from, other related species around this time period.
The chirp produced by P. obscura is a pure tone, transmitted at around 4.7 kHz – well within the range of human hearing.
In addition to helping researchers understand what the insect world was like when dinosaurs roamed the Earth around 145 to 201 million years ago, the results also suggest that the first such insects were limited to frequencies below 20 kHz.
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This is important because other species of Prophalangopsy known today evolved to be flightless, using their wings exclusively for sound production and attracting a mate. These evolved species have also evolved ultrasonic sound-producing organs to help deter predators on the ground.
This P. obscura retained its ability to fly – even over short distances – and did not develop ultrasonic abilities, suggests that it followed a different evolutionary path than other species still extant today, providing further insight into the evolution of this species and its relatives.
But how to hear an insect dead for 150 years?
Like grasshoppers and their relatives, P. obscura, produced a sound by scratching one of its wings with a “file” (or a row of teeth). These vibrations would then be amplified by special structures inside the insect’s wing and radiated into the surrounding environment.
Scientists from the University of Lincoln, the Natural History Museum in London, UK, and Karl-Franzens University in Graz, Austria, used a technique called micro-scanning Laser-Doppler Vibrometry ( LDV) to scan and then reconstruct the wings and produce sounds. holotype organs. They then applied the knowledge of the species’ close relatives, they were then able to deduce the “carrier frequency” (the central frequency at which the overall sound reaches its maximum energy).
Due to its low frequency and pure tone, the song P. obscura sung may have echoed all over the Jurassic landscape.
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