Who’s that singing?
The main groups of singing insects are cicadas, grasshoppers, locusts and crickets. Each species produces a distinctive sound. In almost all cases, only the males sing. Depending on the species, they may sing during the day or at night.
Within a family of singing insects, grasshoppers for instance, not all species necessarily sing. On the other hand, some insects stridulate at a frequency so high that their song is practically inaudible to human ears.
Why do insects sing?
Since it is the males that sing, the main purpose is to attract a female to reproduce and ensure the continuity of the species.
Singing also warns other nearby males that belong to the same species. They may keep their distance or even move farther away. In other species, males interpret the sound as an invitation to approach, and they form a chorus loud enough to attract even more females.
Some insects make courting songs, while others sing to warn off other males as they approach. An insect may make a particular distress sound when it is disturbed, for instance if it is touched. Among certain cicadas, this type of sound makes the insects stop singing or fly away.
How do insects produce their songs?
Insects have developed a variety of physical adaptations to produce and amplify their songs. Cicadas are the only insects with an organ intended solely to produce sounds. It is located in the male’s abdomen, and consists of two curved plates called tymbals. They are connected to powerful muscles that deform the tymbals as they contract. The insect rapidly repeats this motion, contracting and relaxing the tymbals, at different frequencies depending on the species, to create its distinctive sound. Its abdomen forms a resonance chamber that amplifies the sound.
Grasshoppers and crickets produce their songs, called stridulation, by rapidly rubbing the inside edges of their slightly raised forewings together. The forewings have special structures to create and amplify sounds.
Locusts sing by rubbing the femur of their hind legs against the edge of their forewings, a bit like when a bow is drawn across the strings of a violin.
Some beetles can also stridulate, by rubbing the rough surface of an organ against a surface with ridges or edges. The body parts they use depend on the species.
Various groups of insects emit sounds that are not songs. For instance, flies, mosquitoes and bumble bees buzz. The larvae of certain beetles also make an audible noise as they bore their tunnels into wood. Click beetles make an audible click when they are turned onto their backs, propelling themselves into the air and falling back on their feet.