148 ADEPUAGA. [BracJii)uiia 



BEACHININA. 



This very distinct tribe is characterized by having the mesosternal 

 epimera very wide, sometimes nearly as large as the episterna ; in some 

 cases the posterior coxee are separated, the first ventral segment being 

 visible between them, but this character is not universal in all the 

 species ; the most peculiar characteristic of the members of the tribe is 

 their power of ejecting from the anus an explosive liquid, which 

 volatilizes as soon as it reaches the air, and has caustic properties, pro- 

 ducing an effect on the skin similar to that caused by nitric acid : an 

 interesting account is given of this peculiarity in West wood's Classifica- 

 tion, vol. i. p. 76. Our common species of Brachinus possesses this property 

 in a marked degree, and has hence been called the Bombardier beetle, 

 but the effect produced is of course much more noticeable in the largo 

 tropical species : the members of the Brachinina have the abdomen with 

 seven or eight visible segments instead of six as is the rule in the other 

 tribes, but, as Dr. Horn points out, the importance of this fact has been 

 much exaggerated ; the explosive fluid ejected by Braddnus does not 

 differ except in degree of strength and chemical action from that ejected 

 as a means of defence by several other Carabidee, and if we examine 

 the species of any of the genera which emit a liquid whether explosive 

 or not (e.g. Galerita, or any of the larger Dryptini), it will be seen that 

 the structure in no way differs from that of Brachinus, except that the 

 latter has a broader sixth segment, which being truncate, or slightly 

 emarginate, allows the genital armature to become more plainly visible, 

 and we thus count more segments. (See Horn, Carabidae, p. 166.) Dr. 

 Horn places the Brachinina at the head of his Harpalinae unisetosa?, but 

 they evidently belong to the Truncatipenne series, from the rest of Avliich, 

 however, they differ in the fact that the head lias only one supra-orbital 

 seta, whereas in all the other genera it is furnished with two. M. 

 Bedel considers them a separate sub-familj'. 



BRACHINUS, Weber. 



This genus contains about one hundred and Mtj species, which are 

 widely distributed throughout the world, a large proportion occurring in 

 tropical regions ; about twenty-five species are found in Europe, of which 

 we possess three as British, two of wdiich are doubtfully indigenous and 

 require further confirmation : the species generally are of very uniform 

 appearance and colour (red head and thorax and bluish elytra) ; they 

 are found under stones and logs, at roots of grass, &c., often in largo 

 colonies. 



I. Elytra unicolorons. 



i. Fostevior angli s of thorax sharp, projecting; striaj on 



elytra broad and well defined, although shallow . . . B. crepitans, L. 



ii. Posterior angles of tliorax blnnt; strife on elytra very 



feeble B. explodens, Duft. 



II. Suture of elytra broadly red behind seutellum . . . . B. sclopeta, F. 



