442 ]\[r. Charles J. Galian on 



results from the rubbing of this face against a process of 

 the metasternum, which projects into a hollow spa.ce lying 

 above it. 



It is a well-attested fact that Gyclirus rostratus, and one 

 or two other species of the same genus of CarctbidiB 

 stridulate loudly, and the late Mr. Frederick Smith went 

 so far as to declare that Cyclirus rostratus stridulates more 

 loudly than any other beetle found in England. One 

 would naturally expect therefore that the stridulating 

 apparatus is well-developed in this species and easily to be 

 seen; but, so far as I can find, nothing that can satis- 

 factorily be regarded as the stridulating apparatus has up 

 to the present time been described. 



The stridulation of C. rostratus is noticed in Kirby and 

 Spence's " Entomology," and is there stated to be produced 

 by the friction of the prothorax against the base of the 

 elytra. On the other hand Mr. T. Marshall, in the " Ento- 

 mological Magazine" for 1833, attributes it to the friction 

 of the lateral edges of the abdomen against a very fine 

 file lying in the epipleural groove along the side of each 

 elytron. Darwin examined the species, but was unable to 

 detect the presence of any rasp or file. Even if such a file 

 as Marshall has indicated did exist, it would, I think, be 

 impossible for it to operate on the edges of the abdomen 

 in such a way as to produce an appreciable sound. As 

 far as I could make out, the elytra play no part in 

 stridulation, and the only structures I could discover at all 

 likely to answer the purpose are situated on the epimeral 

 lobes of the prothorax. These lobes are somewhat larger 

 and more prominent in Cychrus than is usual in Carahidx, 

 and the inner (hidden) face of each is traversed by a series 

 of rather coarse but fairly regular ridges, running approxi- 

 mately parallel to one another in a direction almost at 

 right angles to the longer axis of the lobe. When the 

 prothorax is bent up and down these ridges rub over the 

 sides of the mesosternum, which in their outer part are 

 slightly rugose, and the friction results in the production 

 of sound. By rubbing these parts together in dead 

 specimens I did not succeed in producing more than a 

 feeble sound. But Mr. Bernard Penny, a young ento- 

 mologist interested in the stridulation of beetles, wrote 

 in answer to an inquiry from my colleague Mr. Arrow, that 

 " the noise [of Cychrus rostratus'] seems to me to be pro- 

 duced by the friction of the lower part of the base of the 



