For the past 150 years, the single known specimen of a species of katydid-like insect known as Prophalangopsis obscura has sat quietly in the London Natural History Museum but now some scientists have worked out what it would have sounded like.
A British/Austrian team, used some seriously fancy equipment and an understanding of the physics of insect acoustics to work out what this species would have sounded like when it sang for a mate, giving insight into the ancient insect soundscape of the Jurassic period.
Katydids are grasshoppers and crickets.
This holotype, or single known specimen, is one of only eight remaining species from the 90 or so which were abundant during the Jurassic period.
The research team has shown the sounds produced by this particular insect would have been similar to, although distinguishable from, other related species around this period.
The chirp produced by P. obscura is a pure tone, emitted at around 4.7 kHz — well-within the range of human hearing.
Aside from helping researchers understand what the insect world sounded like when dinosaurs roamed the Earth some 145 to 201 million years ago, the findings also suggest that early insects of this type were limited to frequencies below 20 kHz.
This is important because the other species of Prophalangopsis known today have evolved to be flightless, using their wings exclusively for sound production and attracting a mate. These evolved species have also developed ultrasonic sound production organs to assist in deterring ground-based predators.
That P. obscura retained its ability to fly — even just short distances — and did not develop ultrasonic capabilities, suggests it followed a different evolutionary path to the other species still in existence today, giving extra insight into the evolution of this species and their relatives.
But, how do you hear an insect that has been dead for 150 years?
Like katydids and their relatives, P. obscura, produced sound by scraping one of its wings with a ‘file’ (or row of teeth). These vibrations would then by amplified by special structures within the insect’s wing and radiated out into the surrounding environment.
Scientists at the University of Lincoln, the Natural History Museum, London, UK and Karl-Franzens-University, Graz, Austria used a technique called micro-scanning Laser-Doppler Vibrometry (LDV) to scan and then reconstruct the wings and sound-producing organs of the holotype. They then applied knowledge of close relatives of the species, they were then able to infer 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 sang may have reverberated far and wide across the Jurassic landscape.