Prehistoric katydids sang in single tone

Science : Katydids, crickets, and other arthropods produce their characteristic chirps by stridulation, a process in which they scrape one rough body part against another, writes Sid Perkins for Science. Until now, it was not known whether ancient insects chirped at a single frequency or across a variety of frequencies. A recent analysis of 165-million-year-old katydid wing fragments shows that katydids sang at a single frequency of about 6.4 kilohertz, or about 6400 cycles per second. That tone is about half the frequency created by today’s katydids but within the range of tones generated by living species of crickets. The chirps, which lasted about 16 milliseconds, probably helped the katydids distinguish the calls of their species in a forest filled with the sounds other insects.