Researchers have discovered that certain caterpillars produce whistling sounds similar to a tea kettle when threatened by predators. The study, published in the Journal of Experimental Biology, reveals that sphinx moths and hawkmoths in their larval stage emit faint cries by forcing air through constrictions in their foregut.
Professor Jayne Yack and biologist Conrado Rose-Denadai from Carleton University in Canada conducted experiments by pinching caterpillars with forceps to simulate predator attacks. Using microphones, they found the sounds were loudest around the insects' mouths, indicating an internal origin rather than external body parts.
Further analysis by researcher Craig Merrett showed that the frequencies matched a model for turbulent air flow. The team concluded that the sound occurs when air is forced through narrow passages between the caterpillars' two foregut chambers, similar to the mechanism in a whistling kettle.
However, scientists remain puzzled about how air enters the upper gut, as caterpillars lack lungs and breathe through openings called spiracles. The study advances understanding of insect defence mechanisms, though observing the process in live insects remains a challenge due to their small size and rapid movements.
