Chap. X. COLEOPTERA. 381 



the rasp is seated, according to Leconte, 73 on the dorsal 

 surface of the abdomen. In Oryctes it is seated on the 

 pro-pygidium, and in some other Dynastini, according to 

 the same entomologist, on the under surface of the 

 elytra. Lastly, Westring states that in Omctloplia hrun- 

 nea the rasp is placed on the pro-sternum, and the scraper 

 on the meta-sternum, the parts thus occupying the under 

 surface of the body, instead of the upper surface as in 

 the Lonsncorns. 



We thus see that the stridulatinsr organs in the dif- 

 ferent coleopterous families are wonderfully diversified 

 in position, but not much in structure. Within the 

 same family some species are provided with these 

 organs, and some are quite destitute of them. This 

 diversity is intelligible, if we suppose that originally 

 various species made a shuffling or hissing noise by the 

 rubbing together of the hard and rough parts of their 

 bodies which were in contact ; and that from the noise 

 thus produced being in some way useful, the rough 

 surfaces were gradually developed into regular stri- 

 dulating organs. Some beetles as they move, now 

 produce, either intentionally or unintentionally, a shuf- 

 fling noise, without possessing any proper organs for the 

 purpose. Mr. Wallace informs me that the Euchirus 

 longimanus (a Lamellicorn, with the anterior legs won- 

 derfully elongated in the male) " makes, whilst 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 likewise make the grating 



73 I am indebted to Mr. Walsh, of Illinois, for having sent me 

 extracts from Leconte's 'Introduction to Entomology,' p. 101, 143. 



