Pair formation in the lesser wax moth,Achroia grisella(Lepidoptera Pyralidae), is accomplished via male-produced pulses (100 µsec) of ultrasound (100 kHz) attractive to females.A. grisellaare sensitive to a wide range of ultrasonic frequencies, enabling them to hear the echolocation signals of both aerialhawking and substrate-gleaning bats. Both flying and running moths exhibit defensive behaviors, dropping to the ground and cessation of locomotion, respectively, in response to simulated bat echolocations. We determined that femaleA. griselladiscriminate the mating signals of advertising males from bat echolocations on the basis of the faster pulse rates (> 60 sec−1) of mating signals. Terrestrial defensive behavior is elicited by a slow rate of lengthy (≥ 1 msec) pulses, features of most searching phase bat echolocations.