736 Mr. Gilbert J. Arrow 07i 



pointed horny tubercles (the plectra), while the actual 

 stridulatory plate is on the second joint (trochanter) of 

 the hind-leg. This joint has undergone a great develop- 

 ment to adapt it to the purpose. It is drawn out into a 

 slender process, so that the succeeding joint seems to arise 

 from the middle instead of the end of it, and on its inner 

 side is a curved ridge running its whole length and cut 

 transversely into a large number of sharp-edged plates. 

 According to Schiodto these delicate plates are themselves 

 finely serrated in a rather complex manner. By the 

 movement of the legs described this elaborate instrument 

 is drawn across the tubercles upon the coxa of the pre- 

 ceding leg in a direction at right angles to the ridges. 



An apparatus practically the same as this occurs in the 

 larvae of the three other Lucanid genera examined by 

 Schiodte, Dorcus, Platycerus and Sinudendron, but in the 

 last the ridges, although fine and sharp, are less regular 

 than in the others, and the coxal tubercles form rows at 

 the narrow part of the plate in this genus, which is one of 

 the least typical members of the family. We may fairly 

 assume from the constancy of the organ in tliese repre- 

 sentative genera that the same highly-elaborated structure 

 is possessed by the larvae of all the Lucanida3. It is 

 therefore rather strange that the adult beetles are in 

 general dumb. Only a single species has been found 

 to stridulate in this stage of its existence. This is 

 Ghiaso gnat Juts Granti, a large insect found to produce a 

 loud sound by Darwin in South America. Darwin seems 

 to have assumed that the faculty was characteristic of the 

 male only, but this is not the case, for I have found the same 

 apparatus in both sexes. I believe it is peculiar to this 

 single species, and nothing of the same type is found in 

 any other Lamellicorn genus. Just within the external 

 margin of each elytron on the lower side is a thick roll of 

 hard chitin distinguished from the rest of the surface by 

 its reddish non-metallic colour. This roll is deeply and 

 finely divided transversely, so that it has the appearance 

 of being a chain of horny rings. The hind femora are 

 flattened beneath and have a slight upward curvature 

 enabling them to be pressed against the flanges of the 

 elytra, and at the part where the contact occurs each 

 shows several longitudinal scratches of which the edges 

 project sharply. By working the leg of a dead specimen 

 backwards and forwards against the sides the scraping of 



