Aposematic sounds in African moths

In response to tactile stimulation and to ultrasonic pulses such as those of attacking bats, many moths of the family Arctiidae produce ultrasonic clicks. To test the hypothesis that these clicks are aposematic sounds, warning bats of unpalatable prey, African moths of these two families were captured at lights, assayed for clicking responses to tactile and ultrasonic stimulation and placed, together with moths of similar body sizes and other families captured at the same time, in a small cage with sympatric Tadarida pumila bats. Arctiid fragments were sought among the insect remains (mostly moth wings) dropped by free-foraging Hipposideros caffer bats. There were no arctiid wings among them, and the captive bats ate a significantly larger proportion of control moths than arctiids. There were no significant differences by species or sex in the arctiids’ clicking responses to either stimulus or in their palatability to bats. Since the arctiids did dick in response to bat-like stimuli and were clearly less palatable to the bats than the control moths, we conclude that the sounds of these moths can act as aposematic sounds.