Stridulatiiig Organs in Cohoptera. 443 



thorax against a small plate on or about the episternuin, 

 in fact, as far as I can judge, — sternum against episternum. 

 The sound is shrill and clearer than that of Aromia 

 moschata. When held between the finger and thumb, the 

 beetle moved the head downwards and up again, but the 

 sound was only produced on the downward motion. The 

 thorax did not move much." These observations of Mr. 

 Penny go far to show that the structures I have described 

 constitute the true stridulating apparatus of Cyclirus. At 

 the same time I am obliged to admit that the ridges on 

 the epimera are much coarser and less regular, and the 

 lateral edge of the mesosternum appears less efficient as a 

 scraper, than the corresponding structures concerned in 

 the stridulation of other beetles; and I have difficulty in 

 understanding why the sound produced by their action 

 should be shriller and clearer than that made by t'ne 

 Longicorn beetles. 



Hydropliilus ficcu^ makes a clearly audible sound, 

 described to me by Mr. H. Donisthorpe and Mr. F. Terry, 

 both of whom have kept the living insects under observa- 

 tion for a long time, as being a distinct stridulation like 

 that of the Longicorns. During the process of stridula- 

 tion the abdomen was observed to move rapidly, from 

 which it was inferred that the sound was produced by the 

 friction of the abdomen against the elytra. I had previ- 

 ously seen it stated that Hydropliilus makes a kind of 

 rustling noise in that way. But having carefully examined 

 the abdomen and elytra I could find no structures that 

 .seemed at all capable of giving rise by their action to 

 a distinct stridulation. The most likely structures of the 

 kind are very similar in character to the epimeral ridges 

 of Cyclirus, and only slightly different in position, the 

 ridges in Hydropliilus being placed transversely in a small 

 area on each side of the under surface of the pronotum 

 just where the latter j&ts over the outer edge of the 

 mesosternum. 



3. Strididating organs on the mcsothorax and middle legs. 



A stridulating area situated on the mesonotum, median 

 in position and usually undivided, occurs in most of the 

 Longicorn beetles, excepting the Prionid/v, in which it 

 is present in the genus Fhilus only. But in certain 

 genera and groups of genera both among the CeramhycidiG 

 and Lamiidx it is entirely wanting. The ridges are as a 



