The theory that the Luna moth can avoid being eaten by bats by using its tail in a distracting manner was first formulated 112 years-ago. However, it is only now that scientists have been able to demonstrate this theory. The theory runs that the tails of Luna moths helped save the insects from hunting bats by distracting the flying mammals’ sonar.
The Luna moth (Actias luna) is a lime-green, Nearctic Saturniid moth. In Canada and northern regions, the moths can live up to 7 days and will produce only one generation per year.
The function of the North American moths’ tails has long been a topic of scientific study. They are not required for flight and are it is not thought that they play a role in attracting mates. With this latter point, the insects are nocturnal and do not appear to be selective about their sexual partners. It was back in 1903 that entomologist Archibald Weeks suggested that the tails might create air patterns similar to those generated by wings that could confuse bats using echolocation to hunt.
To test this idea, researchers affixed 162 Luna moths to the ceiling with fishing line, then used high-speed infrared cameras and ultrasonic recorders to capture information on eight brown bats attacking the moths. Of the 87 moths with intact tails, around one-third were caught by bats. In contrast, 81 percent of the 75 tailless Luna moths in the study were eaten. The researchers also noted that the bats often aimed for the tails of intact moths, and in the vast majority of these attacks, the moths were able to escape.
Further investigation revealed that the echo signature created by the moths’ tails spinning through the air closely mimics that of wing beats.This suggested that the tails provide a life-saving decoy. By analyzing the tail lengths of related moths, the researchers found that similar tails had evolved independently at least four times.
The experiment has been reported in the journal PNAS. The research is titled “Moth tails divert bat attack: Evolution of acoustic deflection.”
