CHAPTER VII 

 THE FUNDAMENTAL ASPECT OF COLORATION 



Structural Colours, p. 172. Diffraction, p. 174 ; Interference, 

 p. 175 ; Scattering of Light by Minute Particles, p. 179 ; Selective 

 Reflection, p. 180. Pigmentary Colours, p. 183. 1. Chlorophyll and 

 other Derived Pigments, p. 183 ; 2. Hcemoglobin and Allied Pigments, 

 p. 189 ; 3. Pigments of Protein Origin, p. 190 ; 4. Pigments zvith Purine 

 Bases, p. 193. Combination Colours, p. 194, Further Remarks on 

 Insect Coloration, p. 195. Literature, p. 203. 



Insect coloration has attracted a large amount of attention 

 from biologists in connection with the relations of both the 

 individual and the race to the environment. Extensive recourse 

 has been made to the amazing variety of colour patterns and 

 markings of insects with the aim of adding fresh arguments 

 bearing upon the central doctrine of natural selection. The 

 relations of colour phenomena to current biological theories have 

 been repeatedly discussed, and consequently it is not intended to 

 deal with this aspect in the present chapter. Attention will be 

 more especially directed to recent research bearing upon the 

 fundamental phenomena of insect colours and pigments, their 

 derivation, and their significance in the j^hysiological processes 

 of the individual. 



It is well known that insect colours fall very naturally into 

 three groups : (1) structural or physical colours, (2) pigmentary 

 or chemical colours, and (3) combination or physico-chemical 

 colours. 



Structural Colours 



Structural colours are often extremely difficult to elucidate, and 

 the findings of recent research have not in all cases been in general 

 agreement. 



White is usually the result of the scattering of light by reflection 



172 



