Insect Colouring 



white, the dull red and the black of the Sa- 

 cred Beetle. It becomes black on the dorsal 

 surface of the Stercoraceous Geotrupes and 

 the Mimic Geotrupes; and, with a quick 

 change, it turns into amethyst under the belly 

 of the first and into copper pyrites under 

 the belly of the second. It covers the back 

 of Cetonia floricola with golden bronze and 

 the under surface with metallic purple. Ac- 

 cording to the insect, according to the part 

 of the body, it remains a dingy compound or 

 sparkles with reflections even more vivid and 

 varied than those possessed by the metals. 



Light seems irrelevant to the development 

 of these splendours; it neither accelerates 

 nor retards them. Since direct exposure to 

 the sun, owing to the excess of heat, is fatal 

 to the delicate process of the nymphosis, I 

 shaded the solar rays with a screen of water 

 contained between slips of glass; and to the 

 bright light thus moderated in temperature I 

 daily, throughout the period of chromatic 

 evolution, subjected a number of Sacred 

 Beetles, Geotrupes and Cetoniae. As stand- 

 ards of comparison I had witnesses of whom 

 I kept some in diffused light and others in 

 complete darkness. My experiments had no 

 appreciable result. The development of the 

 colours took place in the sunlight and in the 

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