STRIDULATION OF INSECTS. 365 



and that the Cicadcs have theirs enclosed within the abdo- 

 men. Reaumur has given a detailed description of these 

 iiistrumciits in the fourth memoir of the fifth volume of his 

 works, accompanied by explanatory figures. All succeeding 

 writers on the subject have followed this illustrious entomolo- 

 gist in his views respecting these organs. 1 will not repeat 

 what they have said, but content myself with remarking that 

 these instruments are enclosed in an abdominal cavity, divided 

 into two cells by a scaly and triangular partition covered by 

 two cartilaginous plates, somewhat resembling a lid in appear- 

 ance. Each cell, at its junction with the abdomen, presents 

 anteriorly a white and folded membrane, and lower down a 

 tight thin transparent membrane, with iridescent reflections, 

 which Reaumur has called the mirror. 



If that part of the abdomen which corresponds to the cavity 

 is opened from above, on each side another folded membrane 

 is perceived of a hard consistence, and sonorous, which is 

 moved by a powerful muscle, composed of straight and parallel 

 fibres, originating from the scaly partition ; this membrane 

 is the timbal {timhale). In order to play on such a compli- 

 cated instrument, Reaumur says the insect successively con- 

 tracts and relaxes the muscle attached to the drum, which 

 causes it to sound. He thinks that the voice is strengthened 

 in the drum {tambour), and that the only use of this part of 

 the vocal organ is to give loudness to the voice. He thinks 

 that the trochanter prevents the operculum being raised too 

 hifrh whilst the insect is singing. Doubts have been expressed 

 respecting the correctness of this simple explanation of the 

 sung of tlie Cicada; and some entomologists have considered 

 that the air performs an important part in the formation of the 

 voice, and that it is due, at least in great part, to the emission 

 of a rapid stream of air issuing from the stigmata of the meta- 

 thorax, which resounds in the organs described above. 



I have not been able to make the researches I wished on this 

 subject, because the part of the country in which I reside pro- 

 duces very few Cicadce. The most diligent search only fur- 

 nished a small species of the genus Tibicen, Latr., whose voice 

 is very weak ; I could only observe it for a moment whilst it 

 was singing at liberty, and it refused to sing in a tumbler in 

 which I had confined it. The common CicMa is not found in 

 this latitude ; its range is not further north than Bellegarde. 



