STRIDULATION OF INSECTS. 369 



sound-producing genus — Mutilla. Although I have only 

 observed it in Mutilla Europea, I do not doubt that other 

 species may possess the property. In this instance, the sono- 

 rous organ is the smooth and shining scutum of the third seg- 

 ment of the abdomen. When the insect draws up the third 

 segment into the second, the friction of the scutum against the 

 inner border of the second segment, makes a very perceptible 

 noise. This property belongs to both sexes. I believe that Spliex 

 sahulosa, Linn., is also a sound-producing insect. At the end of 

 last autumn (1836), I saw one of these insects busied in making 

 a hole in the sand, on the banks of the Rhone ; its head was 

 in a cavity, the abdomen protruding perpendicularly, and it 

 worked with great activity. At the same time, I heard a 

 monotonous and continued stridulation, which considerably 

 resembled that of a small locust, and somewhat the noise of 

 Syritta pipiens. Having approached very close, in order to 

 observe him, I perceived no motion of the wings or any other 

 member : the jaws alone moved : he flew away, but soon re- 

 turned to the same hole, making the stridulation I had already 

 noticed. I have not since had an opportunity of seeing the 

 insect, so am ignorant of the situation of the sonorous organs. 

 I am inclined to believe there are many sound-producing 

 species yet unknown, and that more attentive observations 

 would enable Entomologists to make further discoveries on this 

 interesting subject. 



Lepidoptera. — It now only remains for me to speak of the 

 Death's-head Sphinx, which emits a plaintive noise, a kind of 

 cry, when it is caught, and also when in a state of liberty. 

 Many conjectures have been made respecting the cause of this 

 noise. Reaumur, in the seventh memoir of the second volume 

 of his works, has especially devoted his attention to the subject. 

 He concludes from experiments he made, that the noise is pro- 

 duced by the friction of the proboscis itrompe) against the palpi. 

 These experiments should be noticed, in order to show the 

 necessity of great care in the manner of drawing conclusions 

 from one's observations, and the impropriety of trusting to one 

 experiment if we wish to avoid errors injurious to science. 

 Reaumur observed a quivering motion in the palpi during 

 stridulation, and that they were pressed against the proboscis, 

 as if to subject themselves to friction : he cut off the palpi, and 

 removed them from the proboscis, so that they could not touch 



NO. IV. VOL. V. 3 b 



