344 THE DESCENT OF MAN. 



Leconte,* on the dorsal surface of the abdomen. In 

 Oryctes it is seated on the propygidium; and;, according 

 to the same entomologist, in some other Dynastini on the 

 under surface of the elytra. Lastly, Westring states that 

 in OmalopUa hrunnea the rasp is placed on the pro-sternum 

 and the scraper on the meta-sternum, the parts thus occu- 

 pying the under surface of the body instead of the upper 

 surface, as in the Longicorns. 



We thus see that in the different coleopterous families 

 the stridulating organs are wonderfully diversified in 

 position, but not much in structure. Within the same 

 family some species are provided with these organs, and 

 others are destitute of them. This diversity is intelligible, 

 if we suppose that originally various beetles made a shuf- 

 fling or hissing noise by the rubbing together of any hard 

 and rough parts of their bodies, which happened to be in 

 contact; and that from the noise thus produced being in 

 some way useful, the rough surfaces were gradually devel- 

 oped into regular stridulating organs. Some beetles as they 

 move now produce, either intentionally or unintentionally, 

 a shuffling noise without possessing any proper organs for 

 the purpose. Mr. Wallace informs me that the Eiicliirus 

 longimanus (a Lamellicorn, with the anterior legs wonder- 

 fully elongated in the male) ^' makes, while moving, a low 

 hissing sound by the protrusion and contraction of the 

 abdomen ; and when seized- it produces a grating sound 

 by rubbing its hind legs against the edges of the elytra." 

 The hissing sound is clearly due to a narrow rasp running 

 along the sutural margin of each elytron; and I could like- 

 wise make the grating sound by rubbing the shagreened sur- 

 face of the femur against the granulated margin of the cor- 

 responding elytron; but I could not here detect any proper 

 rasp; nor is it likely that I could have overlooked it in so 

 large an insect. After examining Cychrus, and reading 

 what Westring has written about this beetle, it seems very 

 doubtful whether it possesses any true rasp, though it has 

 the power of emitting a sound. 



From the analogy of the Orthoptera and Homoptera, I 

 expected to find the stridulating organs in the Colpeotera 

 differing according to sex; but Landois, who has carefully 



* I am indebted to Mr. Walsli, of Illinois, for Laving sent me ex- 

 tracts from Leconte's " Introduction to Entomology," pp. 101, 143. 



