Auditory influences on the flight behaviour of moths in a Nearctic site. I. Flight tendency

Abstract

We investigated the hypothesis that earless moths defend themselves from bats in a southeastern Ontario site by means of their flight behaviour. In this study we assume that the time taken by a moth to initiate flight from a stationary perch (flight tendency) will reflect its overall flightedness throughout the night. We predicted that earless moths would exhibit a reduced flight tendency relative to eared moths because moths at this site are primarily at risk of predation from bats while flying. When grouped, earless taxa displayed a significantly greater mean interval to flight departure than eared taxa. Most species of the earless families Saturniidae, Sphingidae, and Lasiocampidae were more likely to remain stationary and took longer to initiate flight than members of the eared families Noctuidae, Notodontidae, Geometridae, Arctiidae, and Drepanidae. We conclude that for most earless moths the hypothesis of reduced flight defence is supported, but there are exceptions to our results that suggest the existence of other antibat defences (e.g., seasonal isolation in a spring-emerging lasiocampid). The evolution of ears in moths and the potential reproductive costs of not possessing them are discussed.