184 MANDIBULATA. COLEOPTERA. 



facility from either of the kindred species by that inexpressible peculiarity of 

 form, which can only be detected by the tact which Mr. Bicheno has termed 

 empirical. This species unquestionably approaches extremely close to Br. 

 explodens and immaculicornis^ but from Br. glabratus it is obviously distinct, 

 the latter insect being more depressed, and the elytra very obsoletely, or not 

 in the least, costated : the mere occurrence of specimens of Br. crepitans seem- 

 ingly approaching towards the other species by variations of colour and sculp- 

 ture *, is not conclusive evidence of all being referable to one species, which 

 the apparent rarity of Br. glabratus, &c. might induce persons to suppose. 



Page 175. Mr. Wailes acquaints me in a letter, dated 1st inst., that the in- 

 formation which he had given me relative to the capture of PoUstichus fas- 

 ciolatus originated in an error, he having lately had an opportunity of exa- 

 mining the specimen, which is not the insect the owner suspected. 



Oii-. I have endeavoured, as far as possible, to give the characters of the genera 

 in the foregoing pages (and shall continue to follow the same plan) from the 

 appearance of the parts of the mouth in situ, aided by the more obvious 

 external differences, in order to enable the student to ascertain the species 

 v,'ith the least possible injury to his specimens; and I here take the oppor- 

 tunity of remarking upon the great advantage which he will experience, and 

 the ease with which it will enable him to pursue his investigations, if he make 

 it a practice to expand the mouth of at least one specimen of each species, 

 which may be done with the greatest facility while recent, or by merely 

 damping the head with a fine wet camel's hair pencil when dried. 



* The mere elevation or depression of the costae cannot be considered as a dif-- 

 ference of sculpture, neither can the depth or shallowness of the impressed points ; 

 — it is the disposition and number of the latter, or the total absence of the former^ 

 which, in my opinion, constitutes that diagnosis. 



