Songs of Stridulation

 

Immature katydids, called nymphs, are initially wingless. 

As the summer temperatures heat up, songs of singing insects fill the air with a variety of sounds.  Members of the order Orthoptera, including katydids, crickets, and grasshoppers, produce a variety of sounds through stridulation, or the rubbing of one body part against another.  

Differential Grasshopper, Melanoplus differentialis

While grasshoppers typically stridulate by rubbing their hind legs against their closed wings, katydids and crickets have modified bases of their wings in order to produce sound.  Specifically, they have a sharp edge or ‘scraper’ on the upper surface of the hindwing which they rub against a row of bumps or ‘file’ on the underside of the forewing. During sound production, katydids and crickets elevate their wings and move them rapidly back and forth, and the wings vibrate as a result of the scraper rubbing against the file.

Central Texas Leaf-Katydid, Paracyrtophyllus robustus

Unlike Orthoptera, male Cicadas in the order Hemiptera produce sounds through a pair of special ribbed organs or ‘tymbals’ located on sides of their abdomens, just behind their wings. When they contract their muscles, it causes the ribs to bend suddenly, producing a sound that resonates within a large air sac in their abdomen. The distinctive sound that is produced is one of the loudest made by any insect.

Resh Cicada, Megatibicen resh

The use of sound is crucial in courtship, with each species having its own distinct song.  Males attract mates through stridulation, producing a vibration frequency that is species-specific.  Songs are distinguished both by their dominant frequency and the details of their timing patterns. Crickets generally produce musical trills of continuous notes often too fast to count, or short bursts of chirps followed by silence.  

Field Cricket, a species in the Gryllinae family

Katydids and grasshoppers have high-pitched songs, composed of atonal shuffles, rattles, scrapes, buzzes, or ticks.  Some sing more or less continuously while other species have long silences in between periods of singing.  Cicada songs are the most penetrating, as rattling buzzes or harsh trills, often with a pulsating or grinding quality.

Fork-tailed Bush Katydid, Scudderia furcata

While most insect songs are the calling songs of males intended to attract females, these songs are thought to have other functions as well.  Some songs are for courtship once a mate is found, and some serve to attract males to a group chorus or to keep males optimally dispersed within a singing colony.  Aggressive songs can also be heard, when two males encounter each other, or even disturbance calls, when an insect is touched or handled.  Whatever the reason, now is the season to hear the songs of stridulation!