370 GOUREAU ON THE 



it ; the insect was silent : he then removed one of the palpi, 

 and the cries of the insect were faint, as if its musical instru- 

 'ment was imperfect. From these observations he concluded 

 that stridulation is produced in this Sphinx by the friction of 

 these organs. He was led into error by the insect on which 

 he tried the experiments, whose silence and cries happened to 

 coincide with the opinions adopted by this clear-sighted observer 

 on the subject. 



M. Passerini places the sonorous organ in a cavity in the 

 head, continuous with the canal of the truncate proboscis." 

 The air entering into and issuing from this cavity, at the will 

 of the animal, produces the sound. 



M. Larey attributes the cause of stridulation to the rapid 

 emission of air from two cavities of a peculiar nature in the 

 abdomen.^ 



I have not read the works of the two last-named naturalists, 

 and am unacquainted with the reasonings and experiments on 

 which they found their opinion. I have, therefore, only vague 

 indications to direct my researches. In the autumn of 1835, 

 I obtained a Death's-head Sphinx, which having been caught 

 two days and been pierced with a pin, was very weak, and 

 could only utter faint cries, and those but seldom. In order 

 to verify by one experiment the opinions of Reaumur and M. 

 Passerini, I unrolled the trunk, and laying hold of it at its 

 base, with a pair of pincers, so as to hinder the palpi from 

 touching it, and prevent the passage of air through the tube, 

 I raised the insect, which uttered a cry as loud as its weak 

 state would permit. At the same time I attentively observed 

 the palpi, and the white membrane which lines the bottom of 

 the canal in which they repose. I did not see any motion in 

 these parts, nor in any other member of the animal ; which 

 appears to me a proof, that the two authors I have quoted 

 above have not ascertained the cause of stridulation. In order 

 to examine M. Larey's theory, I laid bare the portion of the 

 abdomen underneath the two first segments, and, to my great 

 surprise, was not able to discover the two cavities he speaks 

 of. I ought to say the insect was already dead, in which state 

 these organs commonly escape observation. In 1836 I resumed 

 my researches on a living insect in full vigour. I noticed on 



•* Revue Entomologique, vol. i. p. 173. 

 • Cuvier, lUgne Animal, vol. v. p. 390. 



