446 Mr. Charles J. Grahan 07i 



and to be retained throughout the whole life of the 

 larva. 



It has been stated by Leconte that some of the adult 

 Passalid<v stridulate by rubbing the inner surface of the 

 sides of the elytra over the sides of the abdomen ; but 

 I have not been able to find any true stridulating area in 

 the position indicated by him. The adult LucanidcV are 

 without stridulating organs ; and the species of Gcotrwpes 

 while capable of stridulating loudly do so in a manner 

 different to the larvae. The stridulating organs appear 

 therefore to have arisen quite independently in the larvas 

 of these families. 



Stridulating structures are not known to occur on the 

 middle legs of adult beetles except in those remarkable 

 Longicorns from the Sandwich Islands belonging to the 

 genus Plagithmysus. These beetles not only stridulate in 

 the ordinary manner of Longicorns by moving the edge of 

 the prothorax over a striated area on the mesonotum, but 

 have in addition a stridulating file along the lateral edge 

 of each elytron against which tlicy rub the hind femora ; 

 while there is present also on each of the middle and hind 

 coxse a series of ridges which in some species are very 

 regular and parallel, and are considered by Dr. Sharp, who 

 discovered them, to be true stridulating structures. 



4. Strididating organs on the hind-legs, elytra 

 and abdomen. 



In the species of Geotrupes and Typhoeuii, an oblique 

 ridge on each of the hind coxse is transversely striated, 

 forming a file which scrapes against a ridge in the coxal 

 cavity when the coxa is turned. 



In Hcliocopris the posterior surface of each of the hind 

 coxse exhibits a short transverse elevation marked with a 

 few transverse striae; but the stridulating area proper is 

 on the inflexed part of the first abdominal segment which 

 helps to form the coxal cavity, while the striated ridge on 

 the coxa seems to act chiefly as the scraper. 1 am 

 indebted to Mr. H. E. Andrewes for calling my attention 

 to the stridulation of this genus. He says that some 

 of the large Indian species stridulate very loudly, the 

 stridulation being produced by the motion of the hind 

 coxte in their sockets. I have found it easy to produce a 

 tolerably loud sound in dead specimens by turning the 



