Insect Colouring 



Reaumur in fact calls it la Belle. The flat- 

 tering title is well-deserved. On the black 

 background of the larva, vermillion-red, 

 chrome-yellow and chalk-white 'figure side by 

 side in circles, spots, freckles and stripes, as 

 clearly marked as the glaring patches of a 

 harlequin's dress. 



Let us dissect the caterpillar and apply the 

 lens to its mosaic. On the inner surface of 

 the skin, except in the portions coloured 

 black, we observe a pigmentary layer, a coat- 

 ing here red, there yellow or white. We 

 will cut a strip from this coat of many col- 

 ours, after depriving it of its muscular fibres, 

 and subject it to the action of nitric acid. 

 The pigment, no matter what its hue, dis- 

 solves with effervescence and afterwards 

 yields murexide. Here again, then, it is to 

 uric acid, present, however, in small quan- 

 tities in the adipose tissue, that the caterpil- 

 lar's rich livery is due. 



The black parts are an exception. Un- 

 assailable by nitric acid, they retain their 

 sombre tint after treatment as before, 

 whereas the portions stripped of their pig- 

 ment by the reagent become almost as trans- 

 parent as glass. The skin of the handsome 

 caterpillar thus has two sorts of coloured 

 patches. 



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