Moths Use Anti-Bat Defense For Mating
Researchers have discovered that moths use their defense mechanisms against bats for sexual communication.
Asian Scientist (Jul. 12, 2013) - Researchers have discovered that moths use their defense mechanisms against bats for sexual communication.
Moths are nocturnal insects and bats are their main predator in the night. Therefore, moths probably evolved ears for the defensive purpose of detecting bats that began flying in the night sky 50 – 60 million years ago. Moth ears are sensitive to the bat’s echolocation cries and this allows them to avoid bats on the prowl.
Now, new research published in Scientific Reports reveals that moths may use their sense of hearing, and other defense mechanisms against bats, to communicate about sex.
The researchers from Japan and Denmark studied two species: Asian corn borer moth (Ostrinia furnacalis) and Japanese lichen moth (Eilema japonica). Males of both species use sound to court females – but the methods used are very different.
The Asian corn borer moth’s technique is simpler: it produces sounds similar to the echolocation cry of a hunting bat. Thus the male fools the female to believe that a bat is nearby. She responds by sitting perfectly still in an anti-bat freeze position to avoid the bat’s attention – and now the male can mate with her, while she sits perfectly still.
When the researchers played first the sound of a hunting bat and then the sound of a courting male mating in the laboratory, females responded in both cases by freezing. Females simply could not hear the difference, the researchers conclude.
The male Japanese lichen moth has a more sophisticated method: he also emits a sound that sounds like a hunting bat. But when the researchers played first the sound of the bat and then the sound of a courting male, the females in the laboratory could hear the minute differences in the sounds: they would only mate if the sound came from a courting male.
This means that the evolution of bat defense to sexual communication has gone one step further with the Japanese lichen moth: it has developed a specific recognizable mating signal, while the Asian corn borer moth does not distinguish between sounds from a bat and a courting male.
“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,” said Annemarie Surlykke, a member of the research team.
“Our 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.”
The article can be found at: Nakano et al. (2013) Evolution Of Deceptive And True Courtship Songs In Moths.
Source: University of Southern Denmark; Photo credit: Ryo Nakano.
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