Science & Technology

This Is the Blood-Curdling Scream of an Infuriated Caterpillar

When you think of noisy insects, you probably think of things like cicadas, crickets, and buzzing flies. We're guessing you don't think of butterflies and moths — and even less, caterpillars. But some caterpillars will scream if they're provoked. Here, take a listen.

The Nessus Sphinx Hawkmoth Caterpillar

The Very Angry Caterpillar

Caterpillars might not be known for the sounds they make, but the Nessus sphinx hawkmoth caterpillar is changing all that. When these little bugs are provoked, they respond by rearing back and letting out a mighty scream ... well, as mighty as they can muster, anyway. The actual sound they make is certainly creepy, a hissing steep inhale followed by a percussive report of scratchy burping sounds, but it's not loud enough that it would catch your attention on an afternoon walk. What really makes it surprising is the fact that the caterpillar is "screaming" by expelling air out of its mouth — which is weird, because that's not how it breathes.

The hawkmoth caterpillar makes its sound whenever it's harassed, whether by a hungry bird or a boom mic, and that suggests that the noise is meant to be a defense mechanism. Perhaps any predators are so surprised to find their dinner hissing at them that they leave the little bugs alone. But unlike grasshoppers and cicadas, who make sounds by rubbing or vibrating their rigid exoskeletons, Nessus sphinx hawkmoth caterpillars scream with their mouths. Vocalization has never been observed in caterpillars before. But unlike vertebrate vocals, it doesn't have anything to do with the respiratory system. Instead, these bugs are pulling air into their guts, then expelling it through their mouths. No lungs required.

A Cacophony of Caterpillars

The Nessus sphinx hawkmoth might be the only known caterpillar to literally yell at anyone who harasses it, but it's not the only one that can make a noise when it wants. Actually, it's the fourth we've discovered so far. Other caterpillars use other noise-making methods, though, and they do so for different reasons. Some North American silk moths make clicking sounds by snapping their mouthparts together, and the masked birch caterpillar is known to make a drumming sound with its, er, anus, which summons other caterpillars to help build a protective next of silk. Well, that gives a whole new meaning to buttressing your defenses.

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Written by Reuben Westmaas March 22, 2018

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