The Death Moth's 'Squeak' Is Nerve-Wracking

By R. Siva Kumar - 13 Aug '15 11:00AM

Remember Death's Head Hawk Moth in the horror movie, 'The Silence of the Lambs'? The poor moth is a "night-flying harbinger of doom", with a bad reputation., according to nationalgeographic.

However, its "funny squeak" is its strangest characteristic.

Even as insects make noise by rubbing their external body parts like wings and legs, internally produced insect sounds are rarer, while squeaky noises are known only to some hawk moths.

The death's head moths have been named due to the "skull-and-crossbones pattern on their heads." But how do they make such sounds?

Having recorded them, scientists now identify "a two-part, accordion-like system whose rapid movements produce sound."

The discovery has been reported in The Science of Nature, and confirm the "two-phase sound mechanism" that was described in two studies published in 1920 and 1959.

Those hypotheses have been put through tests with some modern methods, including microcomputed tomography (CT) scanning and X-ray video, says study leader Gunnar Brehm, a zoologist at Friedrich Schiller University Jena in Germany.

First, the team researched Acherontia atropos, one of the three death's head hawk moth species and the only one native to Europe. It found that the insect has two parts to its squeak.

At first, the air is sucked in, which causes a flap between the mouth and throat. This is known as the epipharynx, which will vibrate fast. Next, the air gets expelled with the flap open, which leads to another sound.

"The sound system is an accordion basically, with an inflation and deflation of air," Brehm says.

These movements work at "lighting speed", taking just a fifth of a second for execution.

Moreover, it also explains why the moth raids beehives for honey.

"Honey is much more viscous than nectar, and this could have led to the evolution of the epipharynx that works as a valve," helping the moths to suck up the gooey food," Brehm explained. Hence, it's the same mechanism that helps the moth to create the distinctive sound.

"It was not a big jump to sound production," Brehm says.

Hawk moth expert Ian Kitching, an entomologist the Natural History Museum in London, supports the theory that the way they suck honey shows that this is why they "squeak".

"My guess would be the same, or similar," says Kitching, who wasn't involved in the research. "Muscle movements give rise to both feeding and squeaking."