yQ [September, 



expiration from a hole at the posterior part of the tymbals. A few 

 other theories have been advanced to account for the singing of the 

 Cicadce ; thus Rosel (Insectenbelustigungen, ii, p. 168), and after him 

 Oken, thinks it may occur by the tendon of the motive muscle striking 

 on the tymbal like a plectrum ; others state that the abdomen is rubbed 

 against the thorax, or attribute the sound to wing-percussion. 



But the drumming of the Clcacliclce has claims to be classed as 

 stridulation. First, it is produced by the tymbals, for when these 

 are torn the sound invariably ceases. Messrs. Goureau and Solier, 

 and Dr. Gr. Bennett (Wanderings in New South Wales), agree that 

 the tymbals and their motive muscles are absent in the females, which 

 are mute. Dr. Bennett speaks of the notes of the Australian Cicadce 

 as follows : — " The most common sound is the incessant drumming, 

 but it is not confined to this, the ziz, ziz, ziz, is often interrupted by 

 ohoi, ohoi, ohoi, varied to whocky, whocky, whocky, and the noise 

 ceases. Sometimes a prolonged note of alrite, alrite, alrite, is heard 

 varied to ohoe, ohoe, ohoe, the last note being prolonged, followed by 

 whocky, whocky, whocky, in very shrill tones ; then ziz, ziz, ziz, con- 

 tinues for some time, followed by a sound of yocky, yocky, yocky, 

 after which the din suddenly ceases. I observed them to be capable 

 of modulating the sound and varying its intensity. As soon as the 

 delicate tympanum of the drum was destroyed, the sound ceased, 

 although it had just before been of deafening shrillness." 



Then the elevatory movement of the abdomen is necessary to 

 effect the sound. Goureau says, " I procured some of these insects 

 (C. Jicematodes) in the summer of 1836, on which I made the following 

 observations : — When this insect sings in a box no motion is noticeable 

 in the wings nor in any other part of the body ; when I held it 

 between the fingers in such a way as left the abdomen free, its voice 

 was as strong as usual ; but if I held its body and pressed the opercula 

 against the abdomen, it was dull, faint, and stifled ; if, on the contrary, 

 I raised the abdomen, so as to leave the cavities, which are generally 

 covered by the opercula, open, the voice became unusually loud and 

 strong." The motion of the abdomen regulates the pitch of the note 

 and its intensity, as Cams also remarks, but so in like degree do the 

 vibrations in the springing tymbal. " The tymbal vibrates and alters 

 its form," says Goureau, "passing successively from a convex to a con- 

 cave form ; it is this movement which produces the sound and song. 

 These vibrations are very apparent when the insect sings loudly, and 

 less so when only a faint sound is produced, and when the song is 



