LAMELLICORNIA, 13 



these works a similarly specialised vibratory elevated area or boss 

 upon each side of the ante-penultimate dorsal tergite. In the 

 isolated and peculiar genus Ochodcvus a similar but still more 

 highly specialised structure is found at the same part of the back, 

 in the form of a small, curiously sculptured club-like projection. 



The LuCAKiD.i: seem in the adult stage to be practically voiceless, 

 a single South American species, Cldasognatlius grauti^ being the 

 only one known to stridulate — in this case by drawing the hind 

 femur across a " milled " band at the outer edge of the elytron. 



The only groups of JScaeabtEid.e characterised by a single 

 recurring type of vocal organ are the Geotrupin.e and Orphnin^, 

 in a large pi'oportion of which the hind coxa bears a finely ridged 

 area scraped by the sharp edge of the coxal cavitj^ and the 

 Dtnastin.^, of which many genera have fine transverse ridges 

 upon the propygidium, which by movements of the abdomen is 

 drawn across the hinder edges of the elytra. The latter type is 

 highly developed in the Indian Dliiclicus (fig. 8), the propygidium 



Fig. 8. — Diagrammatic representatiou of the terniinal segments of Bipelicuf: 

 bidens (left) and I), cantator (right), showing the stridulatory ridges. 



of which is considerably produced at the expense of the last 

 segment. In Hcteronychus and related genera a pair of stridula- 

 tory files occurs in the same situation. Other situations in which 

 the' vibratory ridges occur in diiferent Indian genera of Scaeab^id.e 

 are — at the inner edge of the elytron in the two large genera Tro.c 

 and Copris, the vibrations being set up in both cases by the 

 movement of the abdomen ; within the hind coxal cavity iu the 

 great beetles forming the genus Heliocopris, the apparatus being 

 scraped by sharp projections upon the coxa ; and upon the inside 

 of the prosternum in Serica, in which the edge of the mesoaternum 

 forms the other part of the instrument. In the curious little 

 beetles of the genus Ocliodceas mentioned above another quite 

 diflferent apparatus is found. Beneath the elytra on each side of 

 the antepenultimate segment of the abdomen is a minute process, 

 assuming various peculiar shapes in diiferent species, but always 

 studded with teeth or tubercles capable of playing upon a micro- 

 scopically sculptured area upon the corresponding lower surface of 

 the elytron. In some large groups of Lamellicoknia peculiar 

 types of stridulating organs have been found in representatives 

 inhabiting otlier parts of the world, but none as yet iu any Indian 

 representatives. Thus in several South American genera of 

 EuteltN/E a striated plate occurs at the end of the hind femur (and 

 the middle femur also in a few species), the ridges being made to 



