Insects first appeared around 400 million years ago, making them one of the oldest terrestrial animal groups in existence. The earliest insects that existed, were all deaf, as they evolved from sea-dwelling organisms that have no reason to hear the sounds within their surrounding environment. However, in nearly half a billion years time, insects diversified into 900,000 species that have been documented, but this figure probably accounts for less than half of the world’s total insect species. Most people do not realize that most modern insects are also completely deaf. Out of the 30 major insect orders, only nine contain species that are capable of hearing. Amazingly, hearing has evolved more than once in some orders. For instance, the hearing mechanisms in butterflies and moths have evolved six times. Even one of the largest insect orders, beetles, contain very few species that have evolved ears. Of the 350,000 documented beetles species, the very few that possess ears acquired them from a separate line of evolution. Although most insects are incapable of perceiving sound and are completely without ears, researchers are beginning to study insect hearing in order to better understand the anatomy of sound-sensing organs in humans and animals.
The minority of insect species that can hear differ tremendously when it comes to the anatomical location of ears. Mosquitoes and fruit flies possess sound-sensing organs on their antennae. Crickets and katydids have ears on their forelegs. Lacewings have ears on their wings and cicadas, grasshoppers and locusts possess ears on their abdomen. Other insects have ears located on their backs or what approximates a “neck.” Incredibly, moths and butterflies possess ears in numerous bodily areas, including their mouthparts. The little-known bladder grasshopper has three pairs of ears along its midsection and praying mantids have only one single “cyclopean” ear, which is located in the center of their chest. The variety of different physical hearing mechanisms is allowing researchers to better understand how auditory information can be received, transmitted, perceived and produced.
Have you ever noticed an insect or arachnid flee from the sound of your voice or footsteps?
