Clever moths with balls!

Cechenena lineosa - a clever moth!

Bats and moths have been engaged in a natural arms race for nearly 65 million years, each evolving strategies to outwit the other. Scientists have long known that members of the tiger moth family blast bats with ultrasound signals, resembling the echolocation calls bats make as they search for and close in on prey. But tiger moths were assumed to be the only moth group able to imitate the bats' signals.

But now a study has shown that several species of tropical hawkmoths can rasp their genitals against their abdomens to beam out loud ultrasound signals at approaching bats, possibly as a weapon used to throw the hunters off course.

Behavioural ecologist Jesse Barber of Boise State University in Idaho and phylogeneticist Akito Kawahara of the University of Florida in Gainesville went to Borneo to try their luck with hawkmoths, a large family of excellent flyers, many of which are found in the tropics.

When the researchers played bat ultrasound to the hawkmoths, they found that three species (Cechenena lineosa, Theretra boisduvalii and Theretra nessus) that they had captured emitted ultrasound clicks in response.

The purpose of this behaviour is not known. It is thought that the moths' ultrasound perhaps serves as a boastful warning to bats of the hawkmoths' barbed legs and excellent aerial skills. One the other hand, it maybe that the hawkmoths are jamming the bats' sonar, as one species of tiger moth has already been shown to do. Either way, the fact that hawkmoths can also make ultrasound clicks means it is likely that "there are even more insect groups that make sounds back at bats", Barber claimed.