At dusk, A. musicus sings in a Jurassic forest of Northwest China.
Credit: Liliana Castaño-R & Fernando Montealegre-Zapata
A pair of fossilized insect wings is singing loud and clear, thanks to the help of researchers. By analyzing a pair of fossilized wings, researchers have recreated what a 165-million-year-old katydid would have sounded like.
Drum roll … the ancient critters sounded something like today's crickets.
"This is a mating call basically, the male calls to the female and the sound needs to be loud so it goes far, travels long distances and the females listen to the sounds and decide whether or not to go to the male," said study researcher Fernando Montealegre-Zapata, of Bristol University in the United Kingdom.
The fossilized wings, discovered in China, are large, about 2.7 inches long (7 centimeters). This means the insect itself would be about 4 inches (10 cm) long. The researchers compared the insect's fossilized wings with those of 59 modern katydids to figure out what sounds the ancient insect, named Archaboilus musicus, made. [Images and Video of ancient katydid]
"Males have special sound generators in the wing. One wing is modified with a file, a row of teeth, like a file, the other wing has a scraper," Montealegre-Zapata said. "When they close the wings, the teeth of the file produce vibrations that are amplified as sound by the wing membranes."
Based on the researchers' calculations, the ancient katydids were able to sing a pure tone using a single frequency of 6.4 kilohertz that lasted for 16 milliseconds. For comparison, the ultrasonic ringtones kids' sometimes use on their phones (since older people can no longer hear in that range) have frequencies between 14 and 17 kHz.
This tone is fairly low in frequency, which means it can travel farther than other, higher frequency tones. "That would suggest that the animals are using it as a private channel in the noisy forest with all the other animals," Montealegre-Zapata said.
To figure out how often the katydids would have made their calls, the researchers looked to modern insects living in similar environments. They found them in Malaysia, an island without bats. Bats and other predators have pushed katydids to chirp at higher frequencies and with fewer calls per second to avoid being located, the researchers said.
"They have to reduce the rate of calling to avoid the bats listening to them," Montealegre-Zapata said, adding that the higher frequency means the calls won't travel as far so fewer predators will likely hear them. "We used the calling rates of these animals, which have the same body size as our fossil and no bat predation and similar frequencies." The ancient katydid probably sang out a few times every second.
Based on this new finding and other katydid fossils, the high-frequency calls may go back 250 million to 200 million years ago, according to Roy Plotnick, a researcher from the University of Chicago who wasn't involved in the study. "We are pretty safe saying this kind of communication could go all the way back to the Triassic," Plotnick told LiveScience. "In 'Jurassic Park,' they actually had cricket sounds in the background, which is actually pretty realistic."
The study was published today (Feb. 6) in the journal Proceedings of the National Academies of Sciences.