SELF-PRESERVATION. 509 



and others, furnished, some with really large mandibles and others with 

 processes upon the head and prothorax, which, like the mandibles, can 

 meet like tongs, and thus serve as a weapon. This is asserted of the 

 Hercules and its large comrades. Pincers of a different kind, as in the 

 earwig, are likewise doubtlessly arms, but in general their possessors 

 are too weak to wound the larger animals or man with them. The 

 generally known means of defence of the bomb-beetle (Brachynus 

 crepitans) is of a peculiar description : it consists in its ejecting from 

 its anus against its enemy a vapoury moisture accompanied by a slight 

 sound, and which vapour has great resemblance to the gas of aquafortis. 

 It is not yet distinctly known what organ secretes this fluid ; according 

 to some it is the anal glands, which we have considered as kidneys ; and 

 according to others, on the contrary, the ejected gas is nothing else than 

 the air accumulated in the colon. This opinion seems to be the most 

 correct, for in the former we cannot distinctly see how the fluid con- 

 tained in the bladders could so immediately be transformed into gas. 

 Another mode of defence, which we have before mentioned, is allied to 

 this, namely, the ejection of the corrosive juices of the stomach, which 

 we observe in many of the larvae of the Lepidoptera, in almost all 

 Carabodca, and in the grasshoppers. It has evidently for object to 

 deter their enemies, for it is only in moments of danger that insects 

 eject it, and therewith soil their enemies, as in the Grylli, or project it 

 against them, as in the rest. The sharp stinking urine of the Dytici, 

 and the other secretions which we have before mentioned, are cast forth 

 in the moment of danger to check the enemy. 



We have before noticed some peculiar organs of secretion in several 

 larvae, as, for instance, in that of Pieris Machaon, which are projected 

 at the approach of danger : they appear, in fact, to be glandular organs 

 which partly secrete odours and partly liquids, for the purpose of 

 chasing the enemy. In P. Machaon the furcate organ lies in the neck, 

 between the head and prothorax, and the same in Doritis dpollo. In 

 the larvae of Harpy a vinula it projects from the tail, in the form of a 

 filament ; and in the larvae of the Tenlhredonodea they lie between the 

 five anterior pair of ventral feet, and are wart-shaped, transpierced pro- 

 tuberances, which project only during danger, and then emit a peculiar 

 odour. In other larva? they lie upon the back, as in the caterpillar of 

 Lip chrysorrhea. Among the beetles similar organs are found in the 

 genera Cantharis and Malachius, which in these are seated at the 

 sides of the thoracic and ventral segments, and are likewise projected 



