of the Corneous parts of Insects. 109 



These observations prove that the colour of the bodies of in* 

 sects is owing to substances of the same nature as those which 

 tinge the hair and fur of vertebrated animals. These oils are de- 

 posited on the surface of the horny parts only during the last pe- 

 riod of the life of the chrysalis, for up to that moment the insect is 

 covered with a colourless membrane. 



Of the salts contained in the elytra of insects. 



The elytra of the Cock chaffer contain, according to my experi- 

 ments, three salts, carbonate of potassa, phosphate of lime, and 

 phosphate of iron. Do all the horny parts of insects contain the 

 same salts ? To answer the question, I burnt several scarabasi 

 nasicornes, previously cleansed, and obtained for residuum a smalt 

 mass of white earthy matter, which nearly retained the form of 

 the body. I remarked that all the hairs had a fawn colour, owing 

 to the presence of phosphate of iron. I digested the ashes in 

 water, and obtained a strongly coloured alkaline lie ; nitrate of 

 silver gave a white precipitate with the solution, soluble in nitric 

 acid ; muriate of baryta, also gave a precipitate, soluble in acid : 

 consequently an alcaline carbonate was dissolved in the water. 

 Muriate of platina gave a slight yellow precipitate with the solu- 

 tion — proving the alcali to be carbonate of potassa. 



The portion of ashes, insoluble in water gave, like those of the 

 elytra, a mixture of the phosphate of lime, and phosphate of iron. 

 These observations attest the perfect similitude that exists between 

 the salts contained in the elytra, and those contained in the other 

 horny parts. 



Having remarked, as I have said above, that the hairs of tftei 

 Scarabaeus nasicornis remained yellow after calcination, I wished 

 to ascertain if that be a general character of the hairs of insects, 

 and for this purpose I incinerated a considerable quantity of them, 

 obtained from the bodies of several large peacock moths, (grands\ 

 paons — Bombyx pavonia ? ) But the residuum was a white ash 

 mixed with only some yellow specks, that is, a mixture of much 

 phosphate of lime, with a little phosphate of iron. The first ob- 

 served fact, therefore, was peculiar only to certain insects. Bf 



