Whether it’s the deafening roar of a cicada, the smashing hum of a bee, or the incessant chirping of a cricket, insects are an integral part of summer music. And arthropods have been making noise for hundreds of millions of years. One of the louder groups were the Prophalangopsidae, a group of singing insects that became mainstream during the Jurassic period when about 100 species swarmed around. Although related to modern crickets and katydids, these ancient arthropods left few direct descendants, making it difficult to decipher what these Mesozoic masters sounded like.
However, a unique specimen of Prophalangopsis obscura can help reproduce these lost sounds. The most enigmatic of the eight modern prophalangopsid descendants, P. obscura has never been observed singing in the wild and is only known 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-making devices that are almost indistinguishable from their fossilized ancestors, making it plausible that P. obscura makes the same notes as its extinct relatives. In fact, his latest study of the insect, published Wednesday in the journal PLoS One, suggests that P. obscura’s song resembles the melodies emitted by prophalangopsids for more than 100 million years.
To recreate the sound of P. obscura, Mr. Woodrow and his colleagues focused on the specimen’s wings, which resemble crumpled parchment paper. “The sound system produced is entirely based on the morphology of the grand pianos,” said Mr. Woodrow, who specializes in bioacoustics. In many insects, the wings function as both an instrument and a speaker system. To produce chirps, crickets and katydids rub their forewings together, scraping a toothy vein against a smooth counterpart on the other wing, much like a spoon raking a washboard. Specialized vanes then amplify the grating vibrations to woo potential mates or terrify enemies.
While the wings of the P. obscura specimen were shredded, the noisy sections remained largely intact. To analyze them, the researchers scanned them with lasers to create 3-D digital models. They then had the models undergo a series of sonic tests to recreate the sound, and compared the wing shape to that of modern singing relatives such as katydids to refine the structure of the song.
They were left with a stuttering chirp that sounded like squeaky sneakers. The song hung at about 4.7 kilohertz, a frequency slightly higher than the standard beep of a smoke alarm. This frequency is much lower than the sounds emanating from hump-winged grigs, another modern prophalangopsid found in the Rocky Mountains that looks like beefy crickets. When startled, Grigs emit a squeak that rises in ultrasonic frequencies around 13 kilohertz to deter predators.
According to Fernando Montealegre-Z, one of Mr. Woodrow’s colleagues at the University of Lincoln and author of the study, this low frequency was handy considering most prehistoric prophalangopsids were likely ground-based. “This frequency is the perfect frequency to use near the ground in vegetation — it travels very far without interference,” he said. In comparison, many high-pitched hump-wing grigs radiate their songs from higher perches in trees to avoid their sounds ricocheting off vegetation.
However, mysteries remain as to what these insects sounded like in the days of dinosaurs. According to Kevin Judge, an entomologist who studies cusp-winged grigs at MacEwan University in Canada, fossils and morphology can give researchers limited information about how insects organized their songs. To find out exactly how P. obscura structures its call, researchers would need to observe a living one in the wild. “Do they sing long trills and hums, or are they chirps?” 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.”
Although the results are more like a remix of Jurassic greatest hits, the authors believe that finding out how P. obscura sounded could be helpful in locating other individuals. For example, computer algorithms could help pick 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 is a good place to start. “The whole idea of recreating the song is to be able to hear it out there,” he said.