If ever the Beatles were to be formed again, they would definitely agree to rope in field crickets, the distant rockstar relatives of grasshoppers, into their influential band. The male members of the Gryllidae family are noted in the animal world for the music they make with their forewings. As the sun goes down and the dark is welcome, the musical concert of adult male field crickets goes live. Some sing continuous trills, the others produce periodic chirps to enchant the ladies of their own species for mating.
But what makes this orchestra? The Grylloid males are equipped with an elaborate musical organ on the forewings called ‘stridulation apparatus’, which is a combination of cuticular teeth row called ‘file’ and hardened edges called ‘scraper’. In field crickets, a rhythmic movement of the scraper on the left against the file on the right side produces a musical rattle when the forewings pace up and down. At the center of the forewings, ridges of hardened cuticles bounded by thick veins constitute the ‘mirror’ and ‘harp’. In the nocturnal battle of animal bands, the narrow channel of air between the raised forewings and body wall, as well as the mirror and harp structures, amplify the songs so that they can lure the ladies from distances far away. Although these acoustic singers usually sing on the field, some of them opportunistically perform solo inside the hollow of a tree trunk, the burrow of a termite hill or even the cracks found in old walls. Such habitats have unique structures which can crank up the song’s volume further.
The sound repertoire of these insects is highly complex and influenced by temperature. A single scissoring file-scraper movement forms a sound ‘syllable’ and a group of syllables in succession form pulsating chirps or a steady trill. The chirp and syllable rates and time duration along with the pitch of the male’s song are species-specific, making them ideal candidates to be utilized in bioacoustics. The Grylloid lady lacks the presence of a voice apparatus. She makes the final jump to the location of the lovelorn male of her interest after hearing him through ears located on her legs! The amorous male may compose a soothing love tune for her once she arrives for a date or plays a rather aggressive Metallica to warn and ward-off other males from his claimed one.