With the exception of flying insects, very few insect species produce audible sounds. Even when insects are ravenously consuming food, their tiny size makes their chomping sounds imperceptible. It can be safely said that insects are not generally noisy creatures, but there are two moth species that produce sounds by opening their mouthparts during their larval stage. Moth larvae, better known as caterpillars, that belong to the hawk and sphinx moth species can let out a “scream” when being approached or attacked by predators. A recent study confirmed that different caterpillar species produce high pitched sounds, but researchers are still unsure as to how some caterpillars are physiologically adapted to produce these sounds.
Researchers gathered a variety of moth species in order raise their caterpillar offspring in laboratory conditions. Once the caterpillars were grown, lead researcher, Conrado Rosi-Denadai, a biologist at Carleton University, attached tiny microphones to the insects. Once the microphones were attached, he simulated a predatory attack against the caterpillars by pinching them with forceps directly behind their heads. The researchers noted that the sounds were loudest near the caterpillar’s mouths. Furthermore, their mouths remained open the entire time the sounds were being produced. This led the researchers to believe that the sounds were being produced inside of the caterpillars. At this point, the researchers hit a brick wall, as the equipment necessary to monitor an insect’s internal physiological processes does not yet exist.
In an effort to learn more about this ability, one researcher dissected the caterpillar’s throats with the hopes of finding anatomical structures that could facilitate sound production. However, she did not find any such anatomical structures. Another researcher studied the sound waves produced by the caterpillar’s screams and determined that a whistle-like mechanism in the caterpillar’s body produced the sound. This explanation still does not explain how caterpillars retain the amount of air needed to produce their screams. Research into this phenomenon is currently ongoing.
Have you ever heard any insect make noise, with the exception of flying insects?