Chap. X. 
COLEOPTERA. 
381 
the rasp is seated, according to Leconte , 73 on the dorsal 
sin-face 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 Omaloplia Itrun- 
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, i n s tead of the upper surface as in 
the Longicorns. 
We thus see that the stridulating 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 
hngimanus (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 liind-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 
^tracts from Leconte’s ‘Introduction to Entomology,’ p. 101, 143. 
