Whether it’s a cicada’s earsplitting drone, a bee’s blaring buzz or a cricket’s incessant chirp, insects are a staple of summer’s score. And arthropods have been making a racket for hundreds of millions of years. One of the noisier groups has been the Prophalangopsidae, a suite of singing insects that went mainstream during the Jurassic period when some 100 species clamored about. While related to modern crickets and katydids, these ancient arthropods left few direct descendants, making it difficult to decipher what these Mesozoic maestros sounded like.
However, a one-of-a-kind specimen of Prophalangopsis obscura may help replay these lost sounds. The most enigmatic of the eight modern Prophalangopsid descendants, P. obscura has never been observed singing in the wild and is known solely from a single specimen discovered somewhere in India in 1869 and now housed in the Natural History Museum in London.
But according to Charlie Woodrow, a Ph.D. student at the University of Lincoln in England, the species possesses sound-producing equipment nearly indistinguishable from its fossilized forebears, making it plausible that P. obscura hits the same notes as its extinct relatives. In fact his recent study on the insect, published Wednesday in the journal PLoS One, posits that P. obscura’s song is similar to the tunes emitted by Prophalangopsids for more than 100 million years.
To recreate P. obscura’s sound, Mr. Woodrow and his colleagues focused on the specimen’s wings, which resemble crinkled parchment paper. “The sound system that’s produced is all based on the morphology of the wings,” said Mr. Woodrow, who specializes in bioacoustics. In many insects, the wings act as both the instrument and the speaker system. To generate chirps, crickets and katydids rub their forewings together, scraping a toothy vein against a smooth counterpart on the other wing, similar to a spoon raking a washboard. Specialized wing cells then amplify the grating vibrations to woo potential mates or frighten foes.
While the P. obscura specimen’s wings were tattered, the noise-producing sections remained largely intact. To analyze them, the researchers scanned them with lasers to create digital, 3-D models. They then ran the models through a bevy of sonic tests to recreate the sound and compared the wing shape with those of modern singing relatives, like katydids, to refine the song’s structure.
They were left with a sputtering chirp reminiscent of squeaky gym shoes. The song hung around 4.7 kilohertz, a frequency slightly higher than the standard smoke alarm beep. This frequency is much lower than the noises emitted by hump-winged grigs, another modern Prophalangopsid found in the Rockies, which look like brawny crickets. When startled, grigs emit squeaks that soar into ultrasonic frequencies around 13 kilohertz to scare off predators.
According to Fernando Montealegre-Z, one of Mr. Woodrow’s colleagues at the University of Lincoln and an author on the study, this low frequency came in handy considering most prehistoric Prophalangopsids were likely ground-bound. “That frequency is the perfect frequency to use close to the ground in the vegetation — it propagates really far without interference,” he said. By comparison, many shrill hump-winged grigs emit their songs from higher perches in trees to avoid bouncing their sounds off vegetation.
However, mysteries linger about what these insects sounded like during the days of the dinosaurs. According to Kevin Judge, an entomologist who studies hump-winged grigs at MacEwan University in Canada, fossils and morphology can only tell researchers so much about how insects organized their songs. To figure out exactly how P. obscura structures its call, the researchers would need to observe a living one in the wild. “Are they singing long, trill songs and buzzes or are they chirpers?” said Dr. Judge, who was not involved in the new study. “There’s no physical record of that because it’s all under neuromuscular control.”
Even if the findings are more akin to a remix of the Jurassic’s greatest hits, the authors believe figuring out how P. obscura sounded may help to locate other individuals. For example, computer algorithms could help pick out their low-frequency songs from recordings of forests in northern India, where the lone specimen was likely collected.
Dr. Judge agreed that knowing what to listen for was a great starting point. “The whole idea of recreating the song is to be able to listen for it out there,” he said.