Caterpillars are not usually noisy, but researchers have recently learned that some of the insects create sounds the same way tea kettles create whistling noises.
Sphinx moths and hawkmoths produce whistles and clicks when hungry predators attack them, and scientists now know why.
They published an analysis in the Journal of Experimental Biology that sheds light on the anatomy of caterpillars and the mechanisms that allow them to produce whistling sounds.
Scientists previously did not know how the caterpillars were able to make the faint cries they produce, according to Live Science.
In their caterpillar stages, sphinx moths and hawkmoths emit faint sounds similar to cries when predators approach. Scientists now know why that is, and they’ve compared the creatures to tea kettles in a new report (file photo)
The scientists trapped female moths and raised their eggs in a lab to conduct the new research.
After the caterpillars had matured, Carleton University professor Jayne Yack and biologist Conrado Rose-Denadai ‘attacked’ the insects by pinching them using forceps.
They listened to the noises the creatures emitted with the help of microphones.
Professor Yack told Live Science: ‘We gave them a light pinch right behind their head, and that stimulated a bird or a predator attack.’
By listening to the sounds picked up by the microphones, the researchers discovered the sounds emitted by the caterpillars were loudest around their mouths.
This suggested the sounds came from the creatures’ insides instead of being produced by external bodily features.
The find disproved the theory that the sounds came from the creatures grinding their chewing bits together.
While the observation got the researchers closer to learning how the sounds were produced, it meant the team would have to see the creatures’ insides to fully understand how they made the noises they emit.
But this provided a significant challenge.
Professor Yack explained: ‘Maybe one day it will be possible to observe what’s happening inside a live insect, which is quite small, when something fast is happening.
‘Right now, we don’t have the equipment to do that kind of thing.’
Another Carleton University biologist, Melanie Scallion, dissected a creature’s throat to search for parts that could potentially cause the cry.
When she did not see any such structures, the focus was turned to the sound waves the cries induce.
Researcher Craig Merrett began analyzing these, which eventually led the team to learn exactly how the insects make the noises they make when a predator is among them.
Professor Yack explained: ‘[Merrett] concluded, based on his model, that these frequencies matched the model for turbulent air flow.’
The researchers deduced from this that the sound probably occurs when the caterpillars force air through constrictions that are located between their two foregut chambers.
HOW DO CATERPILLARS ‘SCREAM’?
A new report explains how certain caterpillar species are able to emit cries when predators approach.
Researchers from Carleton University in Canada learned that the creatures make these noises thanks to a process taking place in their guts.
When air is forced through a constriction inside them, they make a screaming sound, which is loudest around their mouths.
Researchers compared this process to that which takes place in tea kettles.
Structures within certain caterpillars’ guts act like tea kettles. Air is pushed through constrictions creating whistling noises inside them, researchers have found (file photo)
However, the process is still somewhat confusing to scientists, who do not understand how air gets into caterpillars’ upper guts.
The insects do not have lungs, and air gets enters their bodies via openings called spiracles.
Caterpillars are typically herbivores. However, some eat insects; a small percentage eat other members of their own species.
Caterpillars are known for having hearty appetites and being a pest to gardeners. As their bodies grow, they shed their skin continuously.
A body part found within their guts allows them to eat a great amount by monitoring potassium levels.
A number of species of moths are most frequently associated with their caterpillar stages because they endanger growing fruits and other produce.
Additionally, caterpillars are known as a source of silk for humans and as a source of food for animals.
This process is similar to that of a kettle making a whistling noise.
When air is traveling through the constriction, the esophagus amplifies certain sound frequencies.
The same effect happens when a person puts their mouth above the opening of a bottle and blows across the bottle’s mouth.
While the discovery clears up much of the mystery surrounding the noise the caterpillars make, researchers are still in the dark about certain aspects of it.
Researchers do not understand how the creatures get air in the upper portions of their guts, according to Professor Yack.
Caterpillars are dissimilar to most vertebrates in that they don’t have lungs. Instead, air gets inside their bodies by way of openings known as spiracles.