Moths Use Hearing Differently When Picking Up Mating Calls
July 8, 2013

Moths Use Hearing Differently When Picking Up Mating Calls

Brett Smith for - Your Universe Online

A joint team of Japanese and Danish researchers has found various moth species taking Salt-n-Pepa's suggestion to the next level -- talking about sex in a variety of ways.

Lepidopterists have thought for years that moths use their sense of hearing to avoid predation from bats. However, the new study, which was published in Scientific Reports, revealed that their tiny ears are also used to detect the mating whispers of other moths.

"We have examined two different moths and seen that they use their ears and behavior quite differently when they communicate sexually," said Annemarie Surlykke, a biology researcher from the University of Southern Denmark (SDU). "There is no reason to believe that other moths do not do it in their own way, too. The variation in how to use these skills must be huge."

Moths were thought to be dumb, but newer research has shown that they can produce very soft sounds to communicate sexually.

In the study, the team looked at the mating habits of two species, the Asian corn borer moth and Japanese lichen moth. Both species developed their sense of hearing to detect bats, but use very different sonic methods in the mating process.

The simpler of the two techniques is used by the Asian corn borer moth. Looking to mate, the male emits a sound similar to the echolocation noise made by a hunting bat. This sound causes the female to believe that a bat is nearby, causing her to remain perfectly still in an attempt to evade detection. This anti-bat freeze pose allows the male to swoop in and mate with his unsuspecting target.

In their experiment, the research team first played a recording of a hunting bat and then the sound of a courting male in a laboratory setting. Female corn borers responded to both sounds by freezing, which the researchers said was a sign that they could not discriminate between the two noises.

Japanese lichen moths use a more complex, if somewhat more romantic, mating ritual. The male emits a similar echolocation sound, but when the researchers played the two sounds for females -- they were able to tell the difference between the two. The more discriminating females would only mate if the sound came from a male moth. The researchers said the Japanese lichen moths have taken sexual communication another step, developing a distinct recognizable mating call.

"The acoustic communication between bats and moths is a textbook example of the interaction between predator and prey," said Surlykke. "However, our studies show how such a system can evolve, so also moths use their ability to hear and produce sounds to communicate sexually and that they have developed many different ways of doing it. It is a beautiful example of evolutionary diversity."

"I am convinced that there is a lot of whispering communication among moths, which is so quiet that it is difficult to detect and therefore we mistakenly think it does not occur," she added. "Or results offer a whole new understanding of the many directions, evolution of sound communication can lead to, on a basis of system that was originally developed for defense against an enemy. This leads to a new understanding of evolutionary processes."