1 66 COLOUR IN NATURE chap. 



" of a modest, almost unadorned green colour " 

 {Insects, p. 302). 



It is impossible to speak of the colours of the 

 Orthoptera without mentioning the remarkable leaf- 

 insects {Phyllium). As is well known these insects 

 exhibit an extraordinary resemblance to leaves both 

 as to structure and colour. They are, however, when 

 hatched not green but red ; after a few days, during 

 which they feed greedily on leaves, the colour be- 

 comes yellow, and after the first moult it is greenish. 

 After this the green becomes more and more intense 

 after every moult (Becquerel et Brongniart), but it is 

 asserted that when dying the colour changes, exhibit- 

 ing the hues of a fading leaf In dried insects the 

 colour is very fugitive. All these characters suggest 

 an origin from the pigment of the food, and MM. 

 Becquerel and Brongniart have sought to prove this 

 spectroscopically. They found that the pigment 

 occurs in amorphous granules in the subcutaneous 

 connective tissues, and that it gives a spectrum 

 closely resembling that of the green leaves upon which 

 the insects feed. As, however, the whole insect was 

 employed for spectroscopic purposes, without appar- 

 ently any effort being made to remove the gut or its 

 contents, the observations are not very conclusive. 

 The frequency in the order of green colours associated 

 with herbivorous habit may suggest that derived pig- 

 ments are common and important in coloration, but, 

 on the other hand, we have cases like that of the 

 species of Mantis where a green colour is not infre- 

 quent, and yet all are purely carnivorous. There 

 seems also nothing intrinsically improbable in the 

 idea that the green colour may be produced by a yellow 



