COLEOPTERA. 



2S9 



a narrow, slightly-raised surface, crossed by very fine, par- 

 allel ribs, sometimes so flue as to cause irridescent colors, 

 and having a very elegant appearance under the micro- 

 scope. In some cases, as with Typhosus, minute, bristly or 

 scale-like prominences, with which the whole surrounding surface 

 is covered in approximately parallel lines, could be traced passing 

 into the ribs of the rasp. The transition takes place by their be- 

 coming confluent and straight, and at the same time more promi- 

 nent and smooth. A hard ridge on an adjoining part of the body 

 serves as the scraper for the rasp, but this scraper in some cases 

 has been specially modified for the purpose. It is rapidly moved 

 across the rasp, or conversely the rasp across the scraper. 



Fig. 25. Necrophorus (from Landols). r. The two rasps, 

 figure, part of the rasp highly magnified. 



Left-hand 



These organs are situated in widely different positions. In the 

 carrion-beetles (Necrophorus) two parallel rasps (r, fig. 25) stand 

 on the dorsal surface of the fifth abdominal segment, each rasp" 

 consisting of 126 to 140 fine ribs. These ribs are scraped against 

 the posterior margins of the elytra, a small portion of which pro- 

 jects beyond the general outline. In many Crioceridse, and in 

 Clythra 4-punctata (one of the Chrysomelidse), and in some Tene- 

 brionidse, &c.,'^ the rasp is seated on the dorsal apex of the abdo- 

 men, on the pygidium or pro-pygidium, and is scraped in the same 

 manner by the elytra. In Heterooerus, which belongs to another 

 family, the rasps are placed on the sides of the first abdominal 



'* Landois, 'Zeitschrift fur wiss. Zoolog.' B. xvii. 1867, s. 127. 



'5 1 am greatly indebted to Mr. G. R. Crotch for having sent me 

 many prepared specimens of various beetles belonging to these three 

 families and to others, as well as for valuable information. He be- 

 lieves 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. Dar- 

 win, finds that Dermestes murinus stridulates, but he searched in 

 vain for the apparatus. Scolytus has lately been described by Dr. 

 Chapman as a stridulator, in the 'Entomologist's Monthly Magazine," 

 vol. vt p. 130. 



