Meet Acherontia atropos, otherwise known as the death's-head hawkmoth.

It gets its name from the sinister-looking skull shape on its back. In many cultures it is thought to be an omen of death.

It was famously featured in the Hannibal Lecter film The Silence of the Lambs, and appears on the poster. In the film, the serial killer Buffalo Bill uses the moths as calling cards, stuffing them into his victims' throats.

It also makes a cute little squeaking noise.

A death's-head hawkmoth will squeak when a hungry predator approaches, and the noise often deters them, according to Gunnar Brehm of the Friedrich Schiller University Jena in Germany and his colleagues.

Despite their fearsome reputation, this noise is about the only defense the moth has. "They have thorns on their legs so if you touch it they can scratch you a little bit," says Brehm. Other than that, they are harmless.

The death's-head hawkmoth is one of only a handful of moths that can make squeaking noises. Plenty of moths can make sound, but they normally do it by rubbing bits of their bodies together – the same way cicadas make that chirruping noise.

Brehm wanted to know how they do it.

They had previously been studied by German biologist Heinrich Prell, who published a paper on the subject in 1920. However, because it was written in German, his findings were largely forgotten.

Brehm has now repeated many of Prell's experiments, and confirmed his ideas about how the moths make their squeaks.

The results are published in the journal The Science of Nature.

Prell thought the moths make their noises in their heads, by inflating and deflating a chamber in its head called the pharynx – roughly equivalent to the back of the throat.

He claimed that the squeak is divided into two phases, the first louder than the second. Brehm has confirmed this.

Prell suggested that the moth first expands its pharynx, drawing air in. As the air comes in it passes over a hardened plate, and this produces a high-pitched rasping sound. Then the pharynx collapses and the air goes out again, making a second noise.

This also seems to be correct. Brehm used high-resolution video technologies to watch the movements of the moth's muscles as it squeaked. He also found that decapitated moth heads still squeaked when prodded.

The moths' ability to squeak may have evolved as a consequence of their unusual diet.

Many moths and butterflies drink nectar, a sugary liquid made by flowers. They suck it up through a tube called a proboscis.

Brehm thinks the hawkmoths have modified their sucking action to make noise. "It's the same mechanism most moths and butterflies have when they take up nectar from flowers," he says.

Unlike other moths, death's-head hawkmoths mostly eat honey, which is thick and gloopy compared to nectar. So Brehm thinks the moths modified their sucking action to allow the viscous honey to flow freely.

Once that was in place, it was an easy step to modify the pharynx a little more, allowing it to make sounds.

To get honey, death's-head hawkmoths enter the hives of honeybees (Apis mellifera).

That is a tricky business, because as we all know, honeybees sting. To protect themselves, the moths produce a chemical that soothes the bees.