254 INSECT ARTIZANS AND THEIR WORK 



dealt with in detail : we can only pick out, almost 

 at random, a few representative species and describe, 

 not too minutely, the nature of their sounds and 

 how these are produced. The species most cele- 

 brated for its song from antiquity is the Cicada, 

 concerning which the Greek poet, Xenarchus, wrote 

 the ungallant couplet that has been quoted almost 

 ad nauseam, possibly ever since it was written : 



" Happy the Cicadas' lives, 

 For they all have voiceless wives." 



The Cicada stands apart from all other insects, 

 indeed from all other animals, in the character of 

 its voice-box. It is not here a case of scraping one 

 file on another, or a file on a drum. There is a 

 special cavity in the thorax, divided into chambers 

 by membranes of different character, and a specially 

 delicate drum or tymbal which is set vibrating by 

 the insect to produce the initial sound. These 

 vibrations are caught up and intensified by the 

 other membranes and the two opercula or shields 

 which cover the entire apparatus on the under- 

 surface of the insect. 



Landois was of opinion that the sound was pro- 

 duced by the lips of the spiracles or external open- 

 ings of the air-passages, vibrating as a current of 

 air was forced through them by the air-tubes. 

 More recently, Powell showed that, though the 

 spiracles may influence the volume of sound by 

 regulating the tension of the air in the chambers, 

 the vibrations are those of the tymbal. set in motion 



