This way of making sound is called stridulation. The vibrations caused by running the scraper along the file are the source of the cricket’s chirp. It rubs the sharp edge of the lower wing, called a scraper, along the file of the upper wing. When it’s time to sing, the male cricket raises both of its wings, with one, typically the right, slightly above the other. The vein has tiny microscopic teeth that stick up called a file. Each of the male field cricket’s two forewings has a vein that runs across the center. The structure, which researchers call a file, is made of chitin, a rigid polymer that makes the exoskeleton of insects. It’s covered in a row of about 85 to 1,000 microscopic teeth, like the edge of a zipper. On the underside of each of the male cricket’s forewings is a protruding vein that runs from side to side. The males’ forewings have special structures for producing sounds that females lack. (Josh Cassidy/KQED)Ĭrickets have two sets of wings - delicate hindwings and tough leathery forewings called tegmen that cover the hindwings when folded at rest. A male variable field cricket runs its forewings together to create its song. He’s written numerous articles about how crickets and their relatives, like grasshoppers and katydids, make sound. “Most people believe they produce the songs with their legs, like grasshoppers do, but that’s a misconception,” said Fernando Montealegre-Z, a professor of sensory biology at the University of Lincoln in the United Kingdom. That’s because the characteristic, repetitive cricket chirp is really a mating call made by male crickets to attract females. Female crickets need to be able to tell the males of their species apart from the males of other species. Weissman isn’t the only one who needs to tell the different species apart. The trend began in the 1950s when researchers with early portable tape recorders learned there were far more cricket species than earlier scientists had realized. “Then once I know which songs a male sings with, and therefore which species he is, I can go back and find physical characters that will usually separate that species from the other species in the immediate area.” “I listen for the songs in an area, decide how many different songs that I can distinguish, and then collect males that makes those songs,” he said. He analyzes their chirps like a studio engineer closely mixing a hit soundtrack. Weissman spends countless evenings making recordings of cricket songs around the Western states. “It turns out song is a good way to differentiate,” Weissman said. So even for one of the nation’s top experts, telling them apart isn’t a simple task. In December, he published his findings in the journal Zootaxa, identifying 35 species of field crickets in the western states, including 17 new species. Weissman has spent the last 45 years working to identify all the species of field crickets west of the Mississippi River. “When I hear an evening chorus, all I hear are the different species,” said David Weissman, a research associate in entomology at the California Academy of Sciences in San Francisco. And because they look so similar, the most common way scientists tell them apart is not by the way they look, as with most animals, but instead, with a more subtle clue - by the sounds they make. Ask most people about crickets and you’ll probably hear that they’re all pretty much the same: just little insects that jump and chirp.īut there are actually dozens of different species of field crickets in the U.S.
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