On the Sound Organs of the Green Cicada, 177 



tors, probably in succession to the subdivisions in the order 

 indicated, and the shrill chirp thus so strangely intensified.* 



The experiments which lead me to assign these respective 

 functions to the different organs are as follows : — 



(1.) The sound was produced without diminution of 

 volume in the living insect: 



(a) When the wings were removed. 

 (hj In the abdomen, when the cephalo-thorax was re- 

 moved. 

 (c) When the hard protecting plates, both upper and 

 lower, were removed. 



(2.) The sound could be produced, though with somewhat 

 less loudness, by irritating or by artificially working the 

 great muscles while fresh in the separated abdomen. 



(3.) The sound was almost entirely lost on slitting the 

 rattle-membranes in the otherwise unmutilated animal. The 

 insect worked there as before, but the charm was broken, 

 and its voice was lost. 



(4.) Vibrations of all the white tension-membranes took 

 place without the sound, but these always vibrated when 

 the sound was given forth, those of the thorax with greater 

 amplitude. The sound was not afiected by even a large 

 rent in the great tension-membranes of the abdomen. Thus 

 these membranes serve probably to give greater freedom of 

 motion to a larger volume of air in the resonators. 



(5.) The corresponding segments of the abdomen in male 

 and female insects are easily recognisable. In both sexes 

 there are five segments, each of which carries a pair of 

 stigmata on the under surface about midway between the 

 middle line and the margin on either side. 



The stigmata of the mesothorax are most prominent; 

 they are provided each with a cover, consisting of a pair of 

 valves, which close and open at irregular intervals, apparently 

 at the will of the animal, like eyelids. 



The stigmata of the metathorax can be seen also with- 

 out any difiiculty in situation exactly corresponding to their 

 position in the mesothorax. A bristle can be passed through 

 a stigma into the air-tube without passing into any of the 



* In a brief note " On the vocal organs of the Cicada," Proe. L.S.N.S.W., 

 August, 1886, Mr. Haswell accepts Eeaumur's theory. He gives no experi- 

 ment, but adds the idea that the strips of which the great muscles are composed 

 act independently or successively. The American authors, as Packard, are 

 orthodox believers in the older view. 



N 



