What is a "Singing Insect"?

In biology, "song" generally refers to a sound made by an animal during its breeding season to attract a mate and/or defend a territory. Among insects, birds, and frogs, it is the males who sing—females are usually silent, or else produce subtle sounds in comparison to the males.

Who is not familiar with the excited breeding choruses of male frogs at winter's end? Or the musical whistled songs of male songbirds staking out their territories in spring and early summer? Well, insects basically do the same.

Chorusing of Frogs

Chorusing of Birds

Chorusing of Insects

As the frogs and birds grow silent with summer's bloom, we become aware of the gradually intensifying chorus of the insect tribe—a cacophonous mixture of chirps, trills, ticks, scrapes, shuffles, and buzzes. These are the high-pitched songs of male crickets, katydids, and cicadas, serenading females of their own species until cold weather dampens the chorus and heavy frost finally brings it to a close.

How Do Male Insects Make Sounds?

The crickets and katydids produce their songs by rubbing their wings together (technically, it is only the fore-wings that are used to make sounds). A file-like structure on the bottom of one wing is rubbed against a sharp edge or scraper on top of the other wing. This method of sound production is called "stridulation." As the file is drawn across the scraper, thin membranes on the wings vibrate rapidly to create the sounds we hear. Some groups, such as the tree crickets, hold their wings straight up when the sing. Others, such as the meadow katydids, elevate their wings only a small amount when singing.

File and Scraper of True Katydid

Singing Handsome Meadow Katydid

Another type of stridulation occurs in the locusts (short-horned grasshoppers). Rather than rubbing their wings together, locusts rub their legs against their wings. Short pegs on the inner surface of the hind-legs are drawn against the stiff outer edges of the hind-wings. Sounds made in this way are typically very soft and difficult to hear. In the eastern and central United States, the stridulations of locusts are rarely heard and are a very minor element of the insect chorus . . . at least to human ears.

Stridulation of Short-horned Grasshopper

One particular group, the band-winged locusts, make clicking or rattling sounds as they fly, often accompanied by flashing of the wings. This phenomenon is familiar to anyone who has taken a walk along a dusty or sandy road in the heat of a summer day. Known as "crepitation" or "wing snapping," these sounds are produced when wing membranes are suddenly popped taut. Wing snapping often occurs during courtship flights (when the snaps might be construed as a form of "song), but may also be used when a locust is frightened from its perch.

Crepitation of Band-winged Grasshopper

The cicadas use an entirely different method to produce their incredibly loud songs. They have a pair of special sound producing organs called "tymbals," located at the base of the abdomen. Inside each tymbal are stiff but flexible ribs supporting a stout membrane. Muscles attached to the ribs pull the tymbal inward, causing it to pop. The tymbal pops again when the tension is released. Rapid contractions and relaxations of the tymbal muscles create the loud, buzzing songs of the cicadas, which are amplified further by a hollow area in the abdomen.

Cicada singing using tymbals

So there you have it. Our native insect musicians employ a number of methods to produce sounds. Crickets and katydids make their myriad of sounds by rubbing their wings together. Many locusts sound off by rubbing their legs against their wings. Band-winged locusts make snapping sounds by popping their wings when they fly. And cicadas buzz intensely with the help of special organs called tymbals. Such are the methods use to create the myriad of insect sounds—the chirps, trills, ticks, scrapes, shuffles, and buzzes that dominate the natural soundscape from mid-summer into fall.