Chap. X.] 



COLEOPTERA. 



367 



nute, bristly, scale-like prominences, which cover the 

 whole surrounding surface in approximately parallel lines 

 give rise to the ribs of the rasp by becoming confluent 

 and straight, and at the same time more prominent and 

 smooth. A hard ridge on any adjoinhig part of the body, 

 which in some cases is specially modified for the pur- 

 pose, serves as the scraper for the rasp. The scraper is 

 rapidly moved across the rasp, or conversely the rasp 

 across the scraper. 



These organs are situated in widely-different positions. 

 In the carrion-beetles (Necrophorus) two parallel rasps (r, 

 fig. 24) stand on the dorsal surface of the fifth abdominal 



Fig. 24— Necrophorus (from Landois) r. The two rasps. Left-hand figure, part 

 of the rasp highly magnified. 



segment, each rasp being crossed, as described by Lan- 

 dois," by from 126 to 140 fine ribs. These ribs are 

 scraped by the posterior margins of the elytra, a small 

 portion of which projects beyond the general outline. In 

 many Crioceridfe, and in Clythra ^-punctata (one of the 

 Chrysomelidoe), and in some Tenebrionida?, etc.," the rasp 



«' 'Zeitschrift fiir wiss. Zoolog.' B. xvii. 1867, s. 127. 



■"• I am greatly indebted to Mr. G. E. Crotch for having sent me nu- 

 merous prepared specimens of various beetles belonging to these three 

 families and others, as well as for valuable information of all kinds. He 

 believes that the power of stridulation in the Clythra has not been pre- 

 viously observed. I am also much indebted to Mr. E. W. Janson, for 

 information and specimens. I may add that my son, Mr. F. Darwin, finds 



