The ears on a South American rainforest katydid’s legs work
nearly the same way human ears do, a new study has found,
showing that animal groups as apparently unrelated as mammals
and insects have evolved with similar body bits. Mammal ears
work in three stages to convert air vibrations to sound. First,
the acoustic waves hit the ear drum, or tympanum, which
vibrates. Second, tiny ear bones boost the volume as the
vibrations travel along to the fluid of the cochlea. Third, the
inner ear’s hair cells turn the vibrations into electrical
impulses that the brain can read as sound. “Thus, two
phylogenetically remote organisms, katydids and mammals, have
evolved a series of convergent solutions to common biophysical
problems, despite their reliance on very different morphological
substrates,” the study said. Susan Lawler, Head of the
Environmental Management and Ecology at La Trobe University,
said it was a wonderful discovery. “Hearing in insects is quite
diverse. They detect sound through a wide variety of mechan