At least 200,000 species sing in ways that are silent to humans. Listen to one of them now
Some creatures are so quiet, they appear to make no sound at all.When a male treehopper calls out for a mate, he shakes his abdomen 100 times a second to produce a low sound that vibrates through the stem of the plant he is standing on. While that sound is audible to other treehoppers — particularly the female treehoppers he's trying to attract — it's outside the frequency that humans can hear.In Love and Rivals, the second episode of Secret World of Sound, we listen in on dime-sized treehoppers in conversation. But how…