The simple ears of months have responded evolutionarily to the varied levels of selection pressure exerted upon them by insectivorous bats. While frequency-matched (syntonic) bats exert the primary pressure that determines where a sypatric moth's best frequency (BF) lies, there are bats that echolocate in mismatched (allotonic) bandwidths forming selection pressures strong enough to warrant increased secondary sensitivity at these frequencies. It is unknown what neural mechanism is used by these insects to broaden their audiograms but for some neotropical moths, external hearing aids provide a mechanical means of obtaining this sensitivity. Recent studies have uncovered social uses for auditory systems in certain moths and these requirements may provide additional selection pressure. Auditory conditions exist in certain moths that should provide a means to study the evolution of this sensory system from its mechanoreceptor origins to its degeneration in the absence of bat predation.