The greater wax moth is a common pest of bee colonies. And, like many moths, it's also a tasty bat food. Bats and moths are locked in an evolutionary arms race: As bats make higher-pitched calls so that their prey can't hear them, moths evolve the ability to listen for higher pitches. Scientists in Scotland wanted to know just how high the greater wax moth's (Galleria mellonella, pictured) hearing goes. The researchers ordered larvae from a company that sells them as treats for bug-eating pets. ("[B]e careful they can be quite fattening so do not overdo it," the Web site warns.) Then they waited for the larvae to pupate and emerge as adults. The team pinned down each moth and played it sounds at 50 to 300 kHz. Moths hear with tympanal membranes, a pair of eardrumlike structures on the thorax. The scientists measured two responses to the sounds: how much the membrane vibrated and the electrical pulse that traveled through the auditory nerve. Most of the moths heard noises as high as 300 kHz, giving them the most sensitive ears in the insect world, the scientists report online today in Biology Letters. In comparison, humans' ears give up by 23 kHz or so and cats top out at about 64 kHz; the highest known bat calls are about 212 kHz. If a moth can hear a bat's ultrasound calls, it should have a better chance of avoiding the menu. Looks like the moths are winning the race—for now.
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