Avoidance of echolocating bats is thought to have been the selective pressure underlying the repeated evolution of bat detecting tympanal ears in moths. This happened repeatedly involving different anatomical regions in various moth families more than 50 million years ago. Surprisingly, the evolution of diurnal butterflies from their nocturnal moth ancestors appeared to have occurred at the same time: day flying and the subsequent radiation of butterflies resulted from a bat avoiding strategy.
Yack JE, & Fullard JH (2000). Ultrasonic hearing in nocturnal butterflies. Nature, 403 (6767), 265-6 PMID: 10659835