Strididating Organs in Goleoptera. 451 



pro-pygidiuin in the males. The species I have selected to 

 be figured (see PI. VII, figs. 5 and 6) in order to show 

 these structures best are Gryptorhynchinas of a genus to 

 which Jekel gave the MS. name of Eupterus. In the 

 males the scraping tubercles are of such a kind as is 

 usually met with in the other stridulating Guradioniclm, 

 but are somewhat more numerous. Those of the female 

 are exceptional in character, they are few in number, of 

 relatively large size, and each is crossed by a series of 

 small ridges (PI. VII, fig. Qh), appearing to be the com- 

 mencement of what would in time develop into complete 

 pygidial files like those present in the females of other forms. 



The stridulating orsjans of the GurculionidcV are on the 

 whole very interesting. They appear to be confined chiefly 

 to the GryptorliyncMnm and a few allied groups, and a 

 more detailed study of them with a view to their use in 

 classification would, I believe, well repay any student 

 working at those groups. 



Stridulating areas are situated on the dorsal side of the 

 abdomen in the genus Necrophorus, in Orydcs and other 

 genera of Dynastichv, in the genera Lcma and Crioccris of 

 the family GrioceridiV, and in the males of the Tenebrionid 

 genus Hcliopathes. 



In Necropliorus they are narrow and strongly raised, 

 forming two very distinct and conspicuous files on the 

 back of the fifth segment. A short transverse ridge on 

 the underside of each elytron just in front of its apex acts 

 as a scraper. In the Dyanastidm they are usually on the 

 pro-pygidium, and as a rule single ; while in Lema, Grio- 

 ceris and Heliopathes they are double, and placed on the 

 pygidium. There are no special scraping ridges on the 

 elytra in Lcma and Crioccris, but in the males of some 

 species of Hcliopathes, as Darwin has already noticed, each 

 elytron is furnished near the apex with a special series of 

 short ridges. Sexual differences in the structure of the 

 stridulating areas have been noticed in the Dynastichv, 

 Darwin finding in three or four species of Oryctes, that the 

 striae are coarser and more regular in the male than in the 

 female. The same kind of difference, but even more pro- 

 nounced, is met with in Garnclonotus, another genus of that 

 family. 



In the water-beetles of the genus Golymhctes, there is a 

 series of short longitudinal or oblique ridges, placed close 

 to the hind border, on each side of the second ventral 

 TRANS. ENT. SOC. LOND. 1900. — PART III. (OCTOBER) 30 



