INTERNAL ANATOMY OF INSECTS. 149 



In other cases these odours are produced by gaseous 

 vapours. That of the Bombardiers (Brachinus) is the 

 most celebrated and remarkable. It is whitish, of a 

 powerful and stimulating odour, very like that exhaled 

 by nitrous acid. It is caustic, producing upon the skin 

 the sensation of burning, and forming instantly upon it 

 red spots which soon turn brown, and which, in spite of 

 frequent lotions, remain several days. It turns blue 

 paper red a . That amiable, intelligent, and unfortunate 

 traveller Mr. Ritchie, whose premature death, when at- 

 tempting to penetrate to the interior of Africa, all lovers 

 of Natural History so deeply lamented, and whose ardour 

 in the pursuit of that science I had an opportunity of 

 witnessing, when, in company with him, Messrs. Savigny, 

 Du Fresne, and W. S. MacLeay in 1817, I visited the 

 forest of Fontainebleau, in a letter to the last-mentioned 

 gentleman 5 , relates that his companion M. Dupont, near 

 Tripoli took a nest consisting of more than a thousand 

 of a species of this genus. " I am making a few experi- 

 ments," says he, "on the substance which they emit 

 when they crepitate, but do not know whether I can col- 

 lect enough to arrive at any conclusion. It made Du- 

 pont's fingers entirely black when he took them. It is 

 neither alkaline nor acid, and it is soluble in water and 

 in alcohol." From this we may conjecture that k formed 

 crystals. 



xi. Phosphorus. On this remarkable secretion I have 

 so fully enlarged on a former occasion c , that here I shall 

 merely add a few observations which Mr. Murray obli* 



3 N. Diet. d'Hist. Nat. iv. 308. 



b Dated Tripoli in the West, January 21, 1819. 



c VOL. II. p. 418. 



