346 
HABITS OF THE ADEFHAGA. 
II. — Internal structure. —Under this head it will only be necessary to notice a 
few points. The length of the digestive tube does not exceed twice the length of 
their body. The oesophagus is short, and is followed by a membrano-muscular 
crop, very well developed and extremely dilatable. This is succeeded by a 
gizzard, oval or rounded, with cellular and elastic parietes, armed internally with 
mobile corneous pieces, proper for trituration, and provided with a valvule at its 
two orifices. The hepatic vessels, four in number, are inserted near the pylorus. 
Respiration is performed through stigmata , or bivalve apertures, and tracheae 
altogether tubular. The nervous system does not differ from that of Coleoptera 
in general.* * * § 
III. — Means of defence.- —These are furnished chiefly by their mandibles, by 
which, however, the Carahacea are unable to injure, except very trivially, Man 
or the larger animals. They are also provided with a secretion of a far from 
agreeable odour, which they exhale when handled; and some of the larger species 
are able to discharge from the abdomen, to a considerable distance, an acrid and 
disgusting liquor that occasions much pain if brought in contact with the eyes 
or the lips.f It is a similar liquid, though of a more volatile nature, which 
causes the peculiar explosion that the species of Brachinus have been so long 
famed for. Mr. Kirby graphically describes the effects of this explosive pro¬ 
perty :— 44 The most common species (Z?. crepitans ),” he remarks, 44 which is 
found occasionally in many parts of Britain, when pursued by its great enemy, 
Calosoma inquisitor , F., seems at first to have no mode of escape ; when suddenly 
a loud explosion is heard, and a blue smoke, attended by a very disagreeable 
scent, is seen to proceed from its anus, which immediately stops the progress of 
its assailant; when it has recovered from the effect of it, and the pursuit is 
renewed, a second discharge again arrests its course. The bombardier can fire 
its artillery twenty times in succession if necessary, and so gain time to effect 
its escape.The odour of the 44 blue smoke” is thought by M. Dufour to have 
a striking analogy to that exhaled by nitric acid. The vapour is caustic, redden¬ 
ing blue (Mr. Kirby says white) paper, and when applied to the skin producing 
a sensation of burning, accompanied with red spots, which pass into brown, and, 
though washed, remain several days. § In the third volume of the Entomological 
Magazine , a correspondent states, that a specimen of Brachinus Graecus on 
immersion in boiling water let off one of its explosions, which caused the water 
to effervesce similarly to a Seidlitz powder. The explosions may be produced 
for some time after the death of the insect by pressing the abdomen near the 
* Uufour in Annal. des Scienc. Natur VIII., p. 36. 
+ De Geer, IV., p. 86 ; Dufour, Recher. Anatom p. 204. 
J Kirby and Spence, Introd. to Ent., II., p. 246. 
§ Annates da Mas., XVIII., p. 70. 
