448 Mr. Charles J. Gahan on 



accurately described these structures, but Erichson was 

 the first to call attention to them. 



Stridulating files situated on the elytra are to be found 

 in Oxychcila, a genus of Cicindeli'd/v, in Blctliisa and Ela- 

 ]-)hrus (family Carahid/e), in Fdobms {Dytiscida}) , in Trox, 

 Copris and Ligyrus (Scarahmdai), in Cacicus (Tenehrionidcv), 

 in several genera of CiirculionidiV, and in a few Frionid;v. 



In Oxychcila a narrow ridge running along the edge of 

 each elytron just above the epipleural fold is very finely 

 and regularly striated in a transverse direction. The stridu- 

 lation, as Lacordaire has noticed, is produced by rubbing 

 the hind femora along these ridges, but he apparently 

 failed to observe that the part of each femur which rubs 

 along the edge of the elytron is also very regularly striated, 

 the striated area forming a narrow strip with the striffi 

 running in a longitudinal direction. In the Heteromerous 

 genus Cacicus, represented by a single species, 6'. amcrica- 

 nus, SoL, the stridulating apparatus is remarkably like 

 that of Oxychcila, each of the hind femora being striated in 

 the same way. But in this genus (see PL VII, fig. 8) the 

 elytral file is placed much higher up on the side and takes 

 a sinuous course. Tlie little transverse ridges of which it 

 is formed are sufficiently strong to be plainly visible to the 

 naked eye, and it is interesting to note that instead of 

 being exactly parallel with one another, they are so set on 

 the different parts of the file that they always correspond 

 in direction with the sti-ise on the femur as the latter 

 rotates when rubbing along the side of the elytron, Lacor- 

 daire, who heard the stridulation in this species, has de- 

 scribed the method by which it is produced, although 

 failing to notice in this case also that the hind femora are 

 longitudinally striate and thus specially adapted for the 

 part they play in the process. From the structure of the 

 parts concerned, one would expect that the stridulation of 

 this species would be particularly loud, but Lacordaire does 

 not appear to have noticed anything specially remarkable 

 in tliis respect. 



A stridulating file runs along the edge of each elytron 

 in some species of Frionid/e (it is best developed in those 

 of the genus Ctcnoscelis) as well as in some of the Ceram- 

 bycid genus Flagithmysus, but in these Longicorn beetles, 

 the hind femora, except in the presence of granules or 

 spines, are not specially adapted to act as scrapers. 



In the stridulation of the Carabid genera Blcthisa and 



