Some evolutionary innovations are so useful that nature keeps on making them. There's the crab; everyone knows nature keeps making crabs. There's the ability to fly, whether by feathers, membranes, or chitin. And, of course, there's the indispensable trick of using one's genitals to scramble the sonar of hunting bats. No, your eyes are not deceiving you. Some moths have evolved the ability to make noise at bats using their genital structures.